Mind flayers pre-date D&D as a concept, used in Lovecraftian fiction but not with that specific name. Gygax came up with the term “mind flayer” as a specific creature, but the book “The Burrowers Beneath” by Brian Lumley and its art inspired his creation heavily in his own words. Plus Lovecraft came up with Cthulhu from his own nightmares.

Chthonians from the burrowers beneath are large squidlike creatures that can psychically dominate and control lesser creatures, and reproduce by parasites in host bodies of other creatures. Not to mention Cthulhu himself who was created before Mind Flayers and is the obvious inspiration as he is a large, soul-eating betentacled humanoid

So I guess it depends on if you use the term “mind flayer” specifically or just pull from the Cthulhu and Lovecraftian mythos more generally