Green’s Dictionary of Slang

blow (off) the loose corn(s) v.

[the image is of sex in a barn; one’s panting blows away loose corn]

to have sexual intercourse.

c.1698		B.E. Dict. Canting Crew.
1725		New Canting Dict.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.