Rotetvåa is the Swedish term for the original use of wingman - i.e. someone assisting the lead pilot in air combat.

However, the term has come to be used colloquially in more social contexts - in both Swedish and English - as someone assisting the lead male when trying to pick up women. I have never heard any other term used in Swedish in this context though, so I would have to say that the English term is to be used here.