LAWFUL-BLANKET, subs. phr. (old).A wife. See DUTCH. Hence BORN ON THE WRONG SIDE OF THE BLANKET = illegitimate; bastard.
1771. SMOLLETT, The Expedition of Humphry Clinker, ii., 185. Tho my father want a gentleman, my mother was an honest woman; I didnt come on the WRONG SIDE OF THE BLANKET, girl.
1815. SCOTT, Guy Mannering, i., 83. This person was natural son to a gentleman of good family Frank Kennedy, he said, was a gentleman, though on the WRONG SIDE OF THE BLANKET.
WET (or DAMP-) BLANKET, subs. phr. (colloquial).Anything or any person that discourages; a DAMPER (q.v.).