Green’s Dictionary of Slang

nob n.2

also knob
[? abbr. SE nobility or nobleman, but 18C Scot. use suggests an alternative – if unknown – ety.; according to Jon Bee (1823), ‘the swell ... makes a show of his finery ... the nob, relying upon intrinsic worth, or bona fide property, or intellectual ability, is clad in plain-ness’]

1. [18C+] a nobleman, a gentleman.

2. [early 19C; 1910s] (Aus.) an expert [from sense 1].

In derivatives

nobbery (n.)

[1990s+] the elite.

nobbish (adj.)

[mid-19C] aristocratic; showy.

In phrases

come the nob (v.) (also come the duke, ...nabob)

[early 19C+] to give oneself airs.

flash the nob (v.)

[mid-19C] (UK Und.) to pose as an aristocrat to defraud tradesmen.

high-nob (adj.)

[1900s] (Aus.) upper-class.

nob in the fur trade (n.)

[mid-19C] a judge.

nob it (v.)

[early 19C] (UK Und.) to use brains rather than brawn to succeed in the world.

nobs’ houses (n.)

[mid-19C] the Houses of Parliament.