Probably contracted from Nymphodorus, as Artemas from Artemidorus (Tit 3:12): Zenas from Zenodorus (Tit 3:13); Olympas from Olympiodorus (Rom 16:15).
Compare Phm 1:2; Rom 16:5; 1Co 16:19; Act 12:12.
His house (αὐτοῦ)
Others read αὐτῶν their (so Rev., Lightfoot, Meyer). Others, as Westcott and Hort, αὐτῆς her, regarding the name as female, Nympha. It is difficult, however, to know to whom the plural can refer. Some explain, Nymphas and his family. Meyer refers it to the brethren at Laodicaea and Nymphas, and thinks that the allusion is to a foreign church in filial association with the church at Laodicaea, and holding its meetings in the same place.