Its source is a Latin expression meaning "The violet flower."
This girl's name is used in French.
Viola is also the name of the alto-voiced member of the string family of instruments, and some girls may be named with this in mind. However, that name was not derived from the Latin term for the tiny purple flower.
Like the related nouns viol and violin, the origins of this look-alike word are obscure. Some authorities suggest these terms originated as imitations of the sonorous sounds produced by stringed instruments.