Overfamiliar is an adjective. The adjective is the word that accompanies the noun to determine or qualify it.

What does it mean to be Overfamiliar?

: exceedingly or excessively familiar: such as. a : so frequently seen, heard, or experienced as to seem dull or unoriginal a movie with an overfamiliar plot …

Is over familiarity a word?

o·ver·fa·mil·iar

adj. Too familiar, as: a.