Green’s Dictionary of Slang

(orig. US) a cowardly, obsequious person, a toady, one who curries favour.

1849		Yale Lit. Mag. 14 144: Boot-licker [Obsolete in College].
c.1850		F.M. Whitcher Widow Bedott Papers (1863) 831: Sweezer’s very intimit with the squire’s folks — a kind o’ bootlicker tew ’em.
1875		Reynolds’s Newspaper 27 June 5/2: What other person but that of a lackey, a boot-licker, a tuft-hunter, a toady and a belly-crawler, could have indited the three descriptions of the Sultan’s interviews.
1882		Nat. Police Gaz. (NY) 18 Nov. 3/1: [T]he boot llcker of the English aristocracy [...] Bronson Howard .
1885		Gloucester Citizen 20 Feb. 3/2: A very scurrilous and blackguard article [...] from the pen of Ouida’s bootlicker, Legge.
1891		Yorks. Eve. Post 14 Dec. 3/3: [It] described all German subjects who cotinued loyal [...] as ‘debased bootlickers’.
1896		Edinburgh Eve. News 2 Dec. 1/2: Mr Rhodes serves up this kind of stuff to his noisy admirers and to the Sotuh African boot-lickers in general.
1907		Ranch (Seattle, WA) 15 Jan. 3/2: Every meber is entitled to at least one fish hatchery, to be condiucted as the private graft of some political bootlicker.
1912		R.W. Brown ‘Word-List From Western Indiana’ in DN III:viii 571: boot-licker, n. One who flatters in order to win favor.
1940		Yorks. Eve. Post 26 Aug. 5/8: The American playwright who [...] branded Charles Lindbergh as one of ‘Hitler’s bootlickers’.
1966		F. Elli Riot (1967) 70: Digging through the records in search of victims: stoolies, boot-lickers, undercover homos.
1979		G. Wolff Duke of Deception (1990) 49: He hadn’t pocketed the savings, wasn’t venal, was just a bootlicker.
1986		M. Petit Peacekeepers 67: Get out of here you brown-nosing bootlicker.
1996		G. Saunders CivilWarLand in Bad Decline 5: She called me a bootlicker, and I told her she’d better bear in mind which side of the bread her butter was on.