Green’s Dictionary of Slang

linen armourer n.

a tailor.

c.1698		B.E. Dict. Canting Crew n.p.: Linnen-armorers c. Tailers.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1826		Bath Chron. 5 Oct. 4/1: The Merchant Tailors[...] (one branch of which was to line the armour [or] under-dress of knights) was also termed linen armourers.