Green’s Dictionary of Slang

carpet knight n.

[orig. a soldier who was dubbed knight at court (thus kneeling on a carpet) rather than in the chaos of a battlefield]

1. [late 16C–19C] (also carpet-captain, carpet-champion, carpet lover, carpet-monger, carpet squire, carpet warrior) a man whose ‘knightly exploits’ concentrate on the boudoir rather than the battlefield.

2. [late 19C] a man who frequents drawing rooms rather than places of work.