Word Origin & History
late 14c., from L. Faunus, a god of the countryside, worshipped especially by farmers and shepherds, equivalent of Gk. Pan. Formerly men with goat horns and tails, later with goat legs, which caused them to be assimilated to satyrs, but they have lately diverged again.
"The faun is now regarded rather as the type of unsophisticated & the satyr of unpurified man; the first is man still in intimate communion with Nature, the second is man still swayed by bestial passions." [Fowler]
The plural is fauni.