(either 3 or 4 syl.) The sea. In classic mythology, the wife of Neptune (Greek, amphi-trio for tribo, rubbing or wearing away [the shore] on all sides).
His weary chariot sought the bowers Of Amphitritë and her tending nymphs.
Thomson: Summer. (1625–6).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894