noun
who; what kind of person
A somewhat old-fashioned or literary way to ask about a person's identity, similar to 何者 (なにもの) but with a rougher or more emphatic tone. Often used in rhetorical or confrontational contexts.
See also: 何者
お前は何奴だ。
Who are you? (rough, confrontational)
この手紙を書いたのは何奴か。
Who wrote this letter? (literary or old-fashioned)
何者 is the modern, neutral term for 'who' or 'what kind of person'. 何奴 is more archaic and carries a rougher, more confrontational nuance.
Compound of 何 (なに, 'what') and 奴 (やつ, 'fellow, person'). The exact historical derivation is uncertain, but it follows a common pattern of forming interrogative pronouns.