The following linguistic insight pertains to homosexuality. We will consider two terms, malakos and arsenokoites (plural malakoi and arsenokoitai).
Malakos (the singular of malakoi) means "soft, fancy, luxurious," when speaking of things. Of a male it connotes effeminacy or homosexuality, particularly the male who allows himself to be penetrated.
Arsenokoites, on the other hand, refers more to the sexual conduct of the homosexual. Etymologically, it combines arsen (male) with koite (bed, and by extension, the marital relationship, as in the derivative coitus).
Paul may have coined the word arsenokoites, based on a phrase in Leviticus 18:22 and 20:13. Paul's OT was the Greek OT. The word is thus not so much a neologism (the jury's out anyway) as it is an obvious reference to a passage on sin that would have been familiar with anyone who read the Greek OT.
For more, please see Q&A 1510.