Awful - used to mean 'worthy of awe'. In Old English, awe meant “fear, terror or dread.” From its use in reference to God the word came to mean “reverential or respectful fear.” By the early 19th century, awful absorbed the negative aspects of the emotion and the word was used to mean frightful or exceedingly bad.

Pretty - In Old English, “pretty” meant crafty and cunning. Later, it took on a more positive connotation: clever, skillful, or able. It could describe something (for example, a speech) cleverly or elegantly made.

Silly - in its earliest uses, it referred to things worthy or blessed; from there it came to refer to the weak and vulnerable, and more recently to those who are foolish.

Naughty - In the 1300s, naughty people had naught (nothing); they were poor or needy. By the 1400s, the meaning shifted from having nothing to being worth nothing, being morally bad or wicked.