Green’s Dictionary of Slang

1. (also jemmy fellow) a dandy.

1667		‘Ballad’ in Wilson Court Satires of the Restoration (1976) n.p.: His Nanny Fopdoodled her jemmy.
1753		Adventurer No. 100 n.p.: The scale, however, consists of eight degrees; Greenhorn, Jemmy, Jessamy, Smart, Honest Fellow, Joyous Spirit, Buck, and Blood [F&H].
1753		Scots Mag. 1 Oct. 18/2: I bespoke a suit of cloaths of an eminent city-tailor [...] I cut off my hair, and procured a brown bob periwig, [and] took care that my pumps were varnished [...] the character that I had just assumed [...] is called a Jemmy.
1760		B. Weatherby Great News from Hell 13: Then came a Group of Bucks and Jemmies, who all claimed Acquaintance with me.
1772		G. Stevens ‘The Blood’ in Songs Comic and Satyrical 139: Macaronies so neat, / Pert Jemmies so sweet.
1784		Wit’s Mag. July 251/1: The scale, however,consists of eight degrees; Greenhorn, Jemmy, Jessamy, Smart, Honest Fellow, Joyous Spirit, Buck, and Blood.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Jemmy fellow, a smart spruce fellow.
1788		G.A. Stevens Adventures of a Speculist I 24: With ladies when jemmys and jessamys mix.
1788		Times 29 Nov. 4: Little Beaux Jemmies, among whom I have the honour to be ranked with the nick-name of, Sir, Puff Cheek-Squat-Bum.
1797		Sporting Mag. Sept. X 288/1: For though these things may read well amongst the juvenile Jemmies in the City, you, Mr. Editor, ought to know, that in the Country we are not very fond of humbug.
1800		W. Whiter Etymologicum magnum 359: To this race of words I must refer our vulgar term Jemmy — A Jemmy Fellow, &c. and our quaint though familiar phrase, Gim-Crack.
1811		Lex. Balatronicum [as cit. 1785].
1825		Microcosm 5 edn 113: The circumstances [...] are the loud whispers, the half-suppressed fits of laughter, and those other nameless rudenesses, which are not so pointed as to bring a Jemmy Fellow into danger of a serious reprimand.

2. a light cane, as carried by a dandy.

1752

Adventurer No. 100 n.p.: [...] I carried in my hand a little switch, which, as it has been long appendent to the character that I had just assumed, has taken the same name, and is called a jemmy [F&H].

3. a shooting coat, a great coat.

1836–7

Dickens Pickwick Papers (1999) 25: If I’d been your friend in the green jemmy — damn me — punch his head — — cod I would.