Celibacy and chastity are synonyms, aren’t they? The dictionary seems to have the same definitions for both. If you look one up in a thesaurus, the other one comes up as a synonym. That is like stating that something is redundant, and it says the same thing!
Lost in Translation
Who would know more about things getting lost in translation than missionaries serving in places other than their passport culture? Such missionaries are keenly aware of trying to explain the concepts of Christianity in cultures which may not even have such a concept, much less have a word for the concept.
Contemporary English has appropriated two different Latin words with different meanings and now uses those two words as synonyms. This results in confusion between the two related concepts. In requiring vows of celibacy for priests and nuns, the Roman Catholic Church also often got chastity as well. However, when Western culture required celibacy of all adolescents, it did not get chastity nearly as often.