Joss is usually a short form of Jocelyn, which was a medieval boys' name. Because of the -lyn ending becoming associated with girls' names, it is now mostly a girls' name in English. In France, the name Josselin is masculine. On a side note, probably currently the most famous male Joss, Joss Whedon (the creator of "Buffy the Vampire Slayer," "Firefly" etc.)'s first name at birth was Joseph.See Also: Joss (girl), Jocelyn