So I take it that the word "partner" came into the Polish language from English because there was no counterpart to it. - it's a non Polish concept. Interesting when that happens. Funniest imported word I found in Polish is seks apil - though I didn't know what it was until I sounded it out!
May 'this young man' be a possible translation? I remember an old Polish film, where soldiers were calling their group as 'Chłopaki' only. I understand that Duo usually needs a literal translation, but the context of 'partner' made me choose 'young man', and now I wonder how much of a mistake it was.