The month of may was named after a MALE god (Maius), so are you saying May should be a boys name? Same with July and March.
Christian was a girls name in the Middle Ages and so was Julian (historical use) yet most people prefer them on boys and think I'm crazy when I consider Julian for a girl. Genders of names can change over time. So yeah, August might have been a male name before it became a month but now it's a month and a word and therefore unisex to me as are many words (Brook, Sky etc). Faith I could definitely see on a boy. As for Violet, no because it has a feminine sound because of the -ette ending. I'm not saying that all word names are gender neutral but August has no distinctive masculine or feminine sound so it works.