Mainly U.S.: from the vocabulary word, which is from Late Latin castitas, a derivative of castus ‘pure, undefiled’. This was favoured by the Puritans in the 17th century, but is now rarely used in the U.K. It came to notice in the late 60s when it was given by the singer and actress Cher Bono to her daughter.
English and French: from Middle English pine, Old French pin, a topographic name for someone who lived by a conspicuous pine tree or in a pine forest. It may also be a Norman habitational name from any of various places named with this word, such as Le Pin in Calvados; in other cases it may originally have been a nickname for a tall man, one thought to resemble a pine tree.