(The fragments below are from essay 'Avalokitesvara and the Tibetan Contemplation of Compassion Karen M. Andrews May 31, 1993 Tibetan Contemplative Traditions.)

"Avalokitesvara" comes from two roots, "avalokita" and "isvara". "Avalokita" means "glance" or "look". "Isvara" means "lord". "Avalokitesvara" has been taken to mean such things as "Lord of what we see", "Lord who is seen", "Lord who is everywhere visible", "Lord who sees from on high", and "Lord of compassionate glances". 
Avalokitesvara does not appear in the earliest texts about bodhisattvas. However, after a while he becomes one of the important bodhisattvas. By the second century C.E., in the larger Sukhavativyuha, Avalokitesvara is described along with Mahasthamaprapta as one of the two bodhisattvas in Sukhavati, the pure land of the Buddha Amitayus. The two of them are described as the source of the light that illumines the pure land. They also teach the devotees of Amitayus, adapting their techniques to the understanding of the listeners. Probably around the fifth century C.E., a full-blown cult of Avalokitesvara emerged. Avalokitesvara evolves into the supreme savior of all suffering beings. He takes on the characteristics of various brahmanic gods, such as Brahma, Visnu, and Siva. Like Brahma, Avalokitesvara is described as the creator of the universe. 
"From his eyes arose the sun and the moon, from his mouth, the wind, from his feet, the earth." 
Descriptions of his physical form become increasingly fantastic. He is described as being enormously large. His face is a hundred thousand yojanas in circumference (a yojana is a few miles long). His body is gold colored. He has a halo in which there are five hundred buddhas, each attended by five hundred bodhisattvas, each attended by numberless gods. From the hair between his eyebrows there flow eighty-four kinds of rays. Each ray contains a vast number of buddhas and bodhisattvas. Each of his ten finger tips has eighty-four thousand pictures and each picture has eighty-four thousand rays which shine over everything that exists. And so forth. 

Bodhisattva Vow

At this point, Avalokitesvara takes precedence over the buddhas. Even the buddhas cannot estimate Avalokitesvara's merit. It is said that just thinking of him garners more merit than honoring a thousand buddhas. Avalokitesvara's rise to prominence may be partially caused by the Mahayana doctrine of the bodhisattva vow. This doctrine says that the most wonderfully compassionate decision is to vow to stay a bodhisattva instead of becoming a buddha, because bodhisattvas can more effectively help other beings become enlightened. 

Because of his compassion, Avalokitesvara has vowed not to become a buddha and slip into nirvana until after all sentient beings are saved from the nearly endless round of suffering in samsara. Instead, he has committed to continued existence so that he can help suffering beings. Avalokitesvara is not the only bodhisattva who has made this vow. However, he embodies the compassionate motivation which led all bodhisattvas to the vow. Thus, valuing the bodhisattva vow leads to valuing Avalokitesvara and everything he signifies. As compassionate action is Avalokitesvara's essence, he is supremely helpful. He can assume any form in order to help sentient beings, and there are descriptions of him appearing as buddhas, brahmanic gods, humans, and animals. In all these forms he does wonderful things to help alleviate the suffering of beings and bring them towards enlightenment. He rescues his followers from fires, from drowning, from bandits, from murder, from prisons. He gives children to female followers who want children. He helps release beings from the three mental poisons of passion, hatred, and delusion. He helpful both on the physical, worldly plain, and on a more psychological or spiritual level. In addition to being the personification of compassion, 
Avalokitesvara has been connected with light more thoroughly than any other Buddhist deity. The stories say that he was created from a ray of light which emanated from Amitabha Buddha. Avalokitesvara is a luminous being of light, and is repeatedly described as radiating light which shines over all sentient beings and over all corners of the universe. Similarly, he sees everything and everyone in all corners of the universe, a fact that is emphasized by his name. His ability to see everywhere is important because it allows him to manifest his compassion everywhere. The light that he emanates everywhere is sometimes described as a representation of the flow of his compassion to all parts of the universe. 

Avalokitesvara in Shree Lanka

The cult of Avalokitesvara also spread to Sri Lanka. This is a little surprising as Sri Lanka primarily follows Theravada Buddhism, while Avalokitesvara was originally a strictly Mahayana conception. In Sri Lanka, he is called Natha, which is an abbreviation of Lokesvaranatha, which means "Lord of the World". He has become identified with the bodhisattva Maitreya, the "future Buddha". He is also seen as being identical with several Hindu gods. Natha is seen as the guardian deity of Sri Lanka, and is reportedly worshipped primarily because he is regarded as a pragmatically useful source of advantages in the phenomenal world.
A Masterpiece of Classical Sinhalese Sculpture, by Dr. Sarath Chandrajeewa, Ph.D.)

Bodhisattva Avalokitesvara appears in the Tiriyaya inscription of about the 8th century A.D. and it is the earliest reference to the Avalokitesvara in Sri Lanka. The inscription mentions Avalokitesvara as 'a member of triad' consisting of the Buddha and Manjusri.Natha seems to have been a very popular and a dominant figure, after the 8th and 9th centuries A.D. 

Avalokitesvara (Natha) is described in the Sri Lankan Sariputra, a Sanskrit work on iconography used by the image makers in the island in the 15th century A.D. Written between the 9th and the 12th century A.D., it is an adaptation of the South Indian Agama tradition. It gives eight different forms of Avalokitesvara which are influenced by the iconographical representations of Hindu gods. S.Paranavitana gives a translation from the original manuscript as follows.

1 Siva Natha

"Of beautiful face, possessing three eyes, adorned with a crown and a bracelet formed of a serpent, holding a rosary, having four arms, a trisula, two hands in the bestowing and protection attitudes, having a robe of tiger's hide and riding on a bull of the colour of conch. Such are the marks of 'Siva Natha'.

2 Brahma Natha

"Having four faces and four hands of a yellow colour, having a crest of matted hair, adorned with a bracelet of jewels, and a sacrificial cord of gold, one hand in the protection attitude, and another holding a book, riding a golden goose. Such are the characteristic marks of 'Brahma Natha'.

3 Visnu Natha

"Having two hands, holding a chank (conch) and a discus, adorned with a crown and a tiara, a bracelet and a golden robe, in colour that of the lily flower (blue) and riding on a garuda bird. Such are the marks of 'Visnu Natha'.

4 Gauri Natha

"With two hands, holding a bunch of flowers, adorned with a diadem and a lotus flower as an earring, of white body and dark green robe, with the lion as vehicle, the 'Gauri Natha' has thus been described in true characteristics."

5 Matsyendra Natha

"Having four hands and three eyes and holding a noose and staff as weapons with a vase and an ablation in the hanh, crest carrying a chunk, a woolen blanket and a necklace, dressed in a red robe, and riding on a pair of fishes. Such is 'Matsyendra Natha'."

6 Bhadra Natha

"With two hands, of a white colour, holding an axe (pharasu) and a cock standard, with a diadem and (vasika) clad in red garments, and peacock as the vehicle. These are the marks of 'Bhadra Natha'.

7 Bauddha Natha

"Two hands, white complexion, the protection and bestowing attitudes of the hands, rosary, a diadem, a white body, dark green robe, and a lotus seat. These are the marks of 'Bauddha Natha'.

8 Gana Natha

"Four hands and three eyes, two hands holding a noose and an elephant goad, the other two hands in abhaya and varada mudras, a golden sacrificial thread, a white robe, girdle and bangles on the limbs, holding a small casket and a rat as the vehicle. These are the marks of 'Gana Natha'.

The above descriptions from Sariputra does not tally with the sculptures of Bodhisattva Avalokitesvara found in Sri Lanka. Images found in the Island represent Avalokitesvara in princely attire. He often carries a lotus and in the front of his makuta there is a little figure of Buddha in a gesture of meditation. Bodhisattva Avalokitesvara constantly appears in Sinhalese art, but only in human form. Tantric types of sculptures with a large number of hands and heads are not found in Sri Lanka.

In the Chander Bhaga Valley of Himachal is the only one temple of the shikhara type is found. It is the famous sanctuary of Trilok Nath, the 'Lord of the three worlds', which is another name for Avalokiteshvara, the popular Bodhisatva.