PIGEON-PAIR

Finding word books isn't all that difficult but locating an interesting one is another matter. Significantly harder is coming across a palatable mass market paperback. This is one of the few that I've ever come across. While most of the categories listed on the cover are below the topic at hand it's not limited to such banalities. This selection is proof of that sentiment.

PIGEON-PAIR 

twins of the opposite sex. 

[British, 1800s, Farmer and Henley]

from Slang and Euphemism ed. by Richard A. Spears