Green’s Dictionary of Slang

gentleman n.

[on pattern of citizen n. (1); alderman n. (5); lord mayor n.1 : smaller and larger versions of the tool]

[late 18C–19C] (US Und.) a crowbar.

SE in slang uses

In compounds

gentleman commoner (n.) [the Oxford version of Cambridge’s fellow commoner n.; commoners, as opposed to scholars, were seen as empty-headed]

[late 18C–early 19C] (orig. Oxford Univ.) an empty bottle.

gentleman-outer (n.)

[early 18C] a highwayman.

gentleman-usher (n.) [? pun on SE gentleman usher of the Black Rod; note Williams: ‘gentleman usher [...] a male attendant on a lady, sometimes providing a sexual or pimping service’]

1. [late 16C–early 18C] the penis; .

2. [17C] a woman’s male companion.

In phrases

do the gentleman (v.)

[1920s] to urinate.

gentleman in blue (and white) (n.) (also gent in blue) [the uniform]

[mid–late 19C] a policeman.

gentleman in brown (n.)

[late 19C] a bedbug.

gentleman in red (n.)

[late 18C] a soldier.

gentleman of... (n.)

see separate entry.

gentleman’s (…) (n.)

see separate entry.

gentleman wants to take a chance (n.)

[1910s] (US short-rder) a plate of hash.

gentleman who pays the rent (n.)

[late 19C] (Irish) a pig.