The phrase 'what-have-you' is a modern English lexicalization of the interrogative clause "what have you?", which was used conversationally to mean "what other things do you have?". By the early 20th century, this conversational fragment became fossilized into a fixed phrase, losing its interrogative force and grammatical structure. It now serves as a convenient placeholder or indefinite extender at the end of an illustrative list, implying "and other things of that kind". Its evolution exemplifies how flexible, everyday speech patterns can solidify into standard idiomatic vocabulary.

This is a fixed idiomatic phrase formed from the common English words 'what', 'have', and 'you'. It functions as a single lexical unit.