(idiomatic,informal, now usually with "of") To marry (a woman), especially if there is an existing sexual relationship.
I thought about just asking Rosalyn to move in with me, but I decided it was time to make an honest woman out of her.
1749, Henry Fielding, Tom Jones, Folio Society 1973, p. 567:
the mother, Mr Jones, Mr Nightingale, and his love, stept into a hackney-coach, which conveyed them to Doctors' Commons; where Miss Nancy was, in vulgar language, soon made an honest woman, and the poor mother became […] one of the happiest of all human beings.
Usage notes
Also with "out of" for "of", especially in US English.
Formerly used where the woman had been dishonoured and the marriage was regarded as correcting this; nowadays used in a jocular fashion.