From Wiktionary, the free dictionary
From ex-young lady, i.e. former girlfriend; see YL.
XYL (plural XYLs)
- (CB radio slang) One's wife.
1967, CQ: the Radio Amateur's Journal, volume 23, numbers 7-12, page 140:Games for the harmonics, (children), YL's and XYL's and the OM's, plus free soda for all.