Saint Tathan (also known as Tatheus) is claimed to be a Celtic saint, who travelled from Ireland to Wales where he founded a Christian church. An alternative claim is that Tathan was female, originating from Britain.
Sorry. Just seen it. Regret none the wiser, but I thought it worth asking. The answer I fancied was Abran, (bar = except with the a advanced), but it doesn't fit your lettering, and there doesn't seem to be any Welsh connection.