Green’s Dictionary of Slang

a mistress.

c.1368		Chaucer Romaunt of the Rose (1532) line 6339: Nowe am I yonge stoute and bolde [...] And with me folwith my loteby To done me solace and company.
c.1426		Audeley Poems 5: He wold here selle that he had bought [...] And takys to hym a loteby [OED].
1701		Harleian Mss. (1809–13) folio 20: A gentyl man hath a wyfe and a hore; And wyves have now comunly Here husbondys and a ludby [F&H].