This is a French name, but it’s actually a form of the Greek mythological name Dionysius. Luckily for your little Dennis, the French form easier to say – and it’s sure as hell easier to spell.
Famous people named Dennis:
Actors Dennis Quaid, Dennis Hopper, Dennis Franz, and Dennis Christopher; comedian Dennis Miller; U.S. Congressman Dennis Kucinich; Nobel Prize winner Dennis Gabor; basketball player Dennis Rodman.
The name will always be synonymous with the lovable-but-mischievous Dennis Mitchell of "Dennis the Menace" fame.