In Portrait of the Artist as a Young Man, the protagonist, Stephen Dedalus, has the following daydream while gazing at a flock of birds:
A sense of fear of the unknown moved in the heart of his weariness, a fear of symbols and portents, of the hawklike man whose name he bore soaring out of his captivity on osier-woven wings, of Thoth, the god of writers, writing with a reed upon a tablet and bearing on his narrow ibis head the cusped moon.
He smiled as he thought of the god's image for it made him think of a bottle-nosed judge in a wig, putting commas into a document which he held at arm's length, and he knew that he would not have remembered the god's name but that it was like an Irish oath.
What is this oath that sounds like "Thoth"? Is it in Gaelic or is it an English colloquialism from Ireland?