Llankadvan 1254, Slangadvan 1278, Llangadeuan 1286, Lan Gadevan 1291, Langadvan c.1291, Thangadeuen 1295, Langadevan 1342, Llangadvan 1535, LL.gadvan kaer einion c.1550-62, ll.gadfan c. 1655, Llangadfan 1836

Llangadfan – 'The church of (St) Cadfan'; Cadfan may derive from either Old Welsh Catman(n) ( derived Brittonic *Catu-mannos) or Catman (from Brittonic Catumandus) 'wise in battle'. He is reputed to have lived in the 6th Century and to have founded the Church at Tywyn Merioneth.