A slang English term for a Guinea or a Sovereign. Thomas Shadwell, in his play, The Squire of Alsatia, 1688 (iii. 1), makes use of the expression, " Let me equip thee with a Quid," and Bret Harte, in his tale, The Ghosts of Stukeley Castle , introduces a stable boy who wishes to sell a three-legged stool for " five quid."
Source: Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)