quilibet

Quilibet, quaelibet, quodlibet, with quidlibet when it stands alone as a noun. Only the front half declines: cuiuslibet, cuilibet, quemlibet, quibuslibet. The -libet is the impersonal verb libet, "it pleases", frozen on the end, so the literal sense is "who you please" - any one you care to pick, chosen at random and with a shrug.

That shrug is the difference from its neighbours. Quisque is "each one" taken distributively; quisquam is "anyone at all" and lives in negatives and questions; quilibet is "any old one", and can carry a faint contempt. Scholastic disputation kept the neuter: a quodlibet was a session at which the audience could put any question they liked, and English still uses quodlibet for a piece of music that stitches together whatever tunes come to hand.