Baybayin was noted by the Spanish priest Pedro Chirino in 1604 and Antonio de Morga in 1609 to be known by most, and was generally used for personal writings, poetry, etc. According to William Henry Scott, there were some datus from the 1590s who could not sign affidavits or oaths, and witnesses who could not sign land deeds in the 1620s. 

There is no data on when this  of literacy was first achieved, and no history of the writing system itself. There are at least six theories about the origins of Baybayin.

Assamese is a variant of Eastern Nagari script, a precursor to Devanagari. This hypothesis states that a version of this script was introduced to the Philippines via Bengal, which evolved into Baybayin. 

The writing system is an abugida system using consonant-vowel combinations. Each character, written in its basic form, is a consonant ending with the vowel “A”. To produce consonants ending with the other vowel sounds, a mark is placed either above the consonant (to produce an “E” or “I” sound) or below the consonant (to produce an “O” or “U” sound). 

The mark is called a kudlit. The kudlit does not apply to stand-alone vowels. Vowels themselves have their own glyphs. There is only one symbol for D or R as they were allophones in most languages of the Philippines, where D occurred in initial, final, pre-consonantal or post-consonantal positions and R in intervocalic positions. 

The grammatical rule has survived in modern Filipino, so that when a d is between two vowels, it becomes an r, as in the words dangál (honour) and marangál (honourable), or dunong (knowledge) and marunong (knowledgeable), and even raw for daw (he said, she said, they said, it was said, allegedly, reportedly, supposedly) and rin for din (also, too) after vowels. This variant of the script is not used for Ilokano, Pangasinan, Bikolano, and other Philippine languages to name a few, as these languages have separate symbols for D and R. 

The original writing method was particularly difficult for the Spanish priests who were translating books into the native language. Because of this, Francisco López introduced his own kudlit in 1620 that cancelled the implicit a vowel sound. The kudlit was in the form of a “+” sign, in reference to Christianity. This cross-shaped kudlit functions exactly the same as the virama in the Devanagari script of India. In fact, Unicode calls this kudlit the Tagalog Sign Virama. See sample above in Characteristics Section. 

Baybayin historically was used in Tagalog and to a lesser extent Kapampangan speaking areas. Its use spread to Ilokanos when the Spanish promoted its use with the printing of Bibles. Related scripts, such as Hanunóo, Buhid, and Tagbanwa are still used today, along with Kapampangan script. Currently, Baybayin itself is experiencing an artistic revival of sorts, used to convey a Pre-Hispanic feeling as well as a symbol of Filipino identity. Most activist groups used Baybayin as part of their logo using the script for the acronyms (such as the Baybayin K for Anakbayan) alongside the use of a baybayin-inspired latin script. Baybayin tattoos and brush calligraphy are growing in popularity. It is also used in the Latest Philippine Banknotes Issued Last Quarter of 2010. The word used in the bills was “Pilipino” and is used not only as artistic design but a security feature. 

Baybayin is a pre-Hispanic Philippine writing system that was widely used throughout the islands before the arrival of the Spaniards. The term Baybayin comes from the Tagalog word, baybay, which means “to spell.” Spanish missionaries first documented it in the 16th century. However, it is believed to have been in use long before then. It was used to write other languages during those times, namely Ilocano, Pangasinan, and Bisaya. 

Baybayin was primarily used for personal correspondence and government record-keeping purposes. It was also used as a sign manual in trade and for temple rituals and ceremonies. Some ancient manuscripts have been found that were written entirely in Baybayin, some containing as many as 4,000 characters.