Seeing Anglo-Saxon origin names like Godwin (originally Godwine), Edwin (originally Eadwine) and Oswin (originally Oswine), I imagine that "Win" could be a modern form of "Wine".
A little advice: as it says here that this is pronounced 'win', I beg you, if you are considering this name, to instead consider the Welsh name Wyn. PLEASE.
https://en.wiktionary.org/wiki/wine#Old_English [noted -ed]