Green’s Dictionary of Slang

cucumber n.¹

a tailor.

c.1698		B.E. Dict. Canting Crew n.p.: Cucumbers, Taylers.
1698		N. Ward London Spy IV 82: In Obedience to the Will of a Cucumber-Cormorant, a Taylor good lord!
1720		in D’Urfey Pills to Purge Melancholy VI 292: A Taylor good Lord, in the Time of Vacation, / [...] / Here a Scratch, there a Stitch, / And sing Cucumber, Cucumber ho.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1764		Foote Mayor of Garrat in Works (1799) I 177: A journeyman tailor! [...] this cross-legged cabbage-eating son of a cucumber, this whey-fac’d ninny.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Cucumbers, taylors who are jocularly said to subsist during the summer, chiefly on cucumbers.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1813		Cheltenham Chron. 27 May 2/3: If I were possessed of only the ninth part of the spirit of a man it would be imposible to avoid answering [...] If this sapient detector of fraud really thinks I did Cabbage the public money, he must allow I cut my cloth to the best advantage [...] permit me, Mr Editor, with the coolness of a Cucumber, to subscribe myself, Your humble servant, WM Hastings, Tailor.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
1835		G. Kent Modern Flash Dict.
[1845		‘Knyghte and the Taylzeour’s Daughter’ in Martin & Aytoun Bon Gaultier Ballads 9: Gaberdines in countless number / Did the taylzeour-knyghte repair! / And entirely on cucumber, / And on cabbage, lived he there].
1890		C. Hindley Vocab. and Gloss. in True Hist. of Tom and Jerry 170: Cucumbers. Tailors, because they are seedy.

In derivatives

cucumberish (adj.)

poor, impoverished.

1821

Egan Life in London (1869) 183: The chap in the corner [...] has been chaffing spendall [...] about his being so cucumberish as to be compelled to gammon the draper.

In compounds

cucumber time (n.)

the summer time; thus a slack period in any job.

1674–81		‘The Trappan’d Taylor’ in Ebsworth Roxburghe Ballads (1891) VII:2 467: It was in the prime of Cow-cumber time, when taylors had very much leisure.
1691		‘The Country Maiden’s Lamentation’ in Ebsworth Roxburghe Ballads (1891) VII:2 475: It was in the season of cucumber-time, when Taylors were sharp at their Needles.
c.1698		B.E. Dict. Canting Crew n.p.: Cucumbers, Taylers. Cucumber-time, Taylers Holiday, when they have leave to Play, and Cucumbers are in Season.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].