1. [mid-18C+] (also mine uncle, mine uncle’s, my uncle, my uncle’s, uncle Monty Pete [i.e. ‘mount of piety', fr. Fr. mont de piété, a pawnbroker] ], Uncle Sam, uncle Tom) a pawnbroker [the avuncular help he gives ‘relatives’ in temporary financial distress].
2. [late 18C–early 19C] (also mine uncle’s) a privy.
3. [mid-19C–1960s] (US, also unkey, unky) a form of address to a black male whose name one does not know or ignores.
4. (Aus.) a money-lender.
5. [late 19C–1910s] as your uncle, oneself.
6. [20C+] a general term of address to a man; there need be neither prior acquaintance nor any form of relationship.
7. [1920s–40s] (US, also auntie) a receiver of stolen goods.
8. [1940s–70s] (US gay/prison) an older homosexual male with a taste for young men or boys.
[1910s+] (US) to beg someone to stop an action, to surrender; also fig.
[late 18C–early 19C] to abandon one’s wife shortly after the marriage ceremony.
[19C] to pawn.
[mid–late 19C] the vagina; thus be where uncle’s doodle goes v., to have sexual intercourse.