He wasn't making up the compound arseno-koitai "male-bedder" out of nothing: he was imitating the Septuagint translation of Leviticus. Leviticus says not to shakav "bed" a male, so the Septuagint unusually turns the Greek word for "bed" into a verb for purpose of translating this verse, and Paul is following that usage.[/quote]
I believe Mit like Mitah is the word for bed... and Shakav means 'to lay.'