Green’s Dictionary of Slang

brown nose n.

also brown snout
[brown-nose v.]

1. (orig. US milit.) a toady, a sycophant.

[US] ‘Citadel Gloss.’ in AS XIV:1 Feb. 25/1: brown nose, n. A cadet who curries favor.
[US](con. 1944) N. Mailer Naked and Dead 61: Stanley is the biggest goddam brown-nose in the platoon.
[UK]I, Mobster 79: We want our own investigators for this neighbourhood, not a bunch of goddamned brown noses.
[US]D. Westlake Busy Body 31: That’s the kind of guy you are. [...] Brown-nose.
[US]T. O’Brien If I Die in a Combat Zone (1980) 42: ‘Want me to polish the damn thing with a sock?’ ‘Use yer brown nose,’ the Montanan drawls.
[US](con. c.1967) J. Ferrandino Firefight 149: Watts here is the Cougar Company brown nose.
[US]B. Hamper Rivethead (1992) 207: He couldn’t make a move without [...] loud chants of ‘suckass’ and ‘brown snout’ ringin’ in his ears.
OnLine Dict. of Playground Sl. [Internet] brown nose n. a ‘crawler’ or sycophant. Gets the brown nose from having it stuck up another person’s bum while ‘arse-licking’.

2. attrib. use of sense 1.

[US]F. Paley Rumble on the Docks (1955) 315: What a brown-nose job the bulls can do when you are nice.
[US]K. Brasselle Cannibals 194: I’d had Irving call his brown-nose announcer and warn him.
[Aus]Bug (Aus.) 24 Feb. [Internet] They should rename it the Brownnose Medal and give it to whoever comes out with the most idiotic statement of the season.
[UK]Brummagem Dict. [Internet] : earhole n. a creep; a brown-nose.

In phrases

have a brown nose (v.)

to be a sycophant.

[US]Mad mag. Apr. 36: I’ll wear a suit and nose of brown.
[US]Maledicta 1 (Summer) 16: Naturally, he is also a sycophant and toady to the boss: [...] He has a brown nose and a fur tongue, or is a T.L. (tokus-leker: Yiddish), and the boss’s automatic tongue-wiper.
one’s nose is always brown

said of a dedicated sycophant.

trish9095 posting about article by Therese Droste ‘Do It Your Way’ on Monster Admin/Support Forum 8 Nov. [Internet] The reason the brownnoser’s ‘nose’ is always brown is for the simple fact they ‘keep their nose’ so far up managements ass, they tend to eat, smell and live the BS they produce.