The Oxford Names Companion, OUP "Scottish Forenames" - Donald Whyte, FGH, FSG
Chambers Dictionary [2003]
Notes:
English and Italian, from the Roman family name [Camillus:m], derivation unknown. Chambers suggests it could be the title of a free-born attendant at a sacrifice; Virgil named a queen of the Volsci tribe Camilla.
Thanks to Donald Whyte who provided much of the initial information for this site.