Recorded as an epithet of Poseidon in ps.-Herodian, Epimerismi 147.10, who etymologizes it as o( foitw=n e)n th=| a(/lmh| ("he who wanders in the brine"). Apart from the derivative entry in ps.-Zonaras 1827.12-13, the word is not attested elsewhere. Adler refers to phi 874, futa/lmios ('nourishing'/'at birth'), implying that the current headword is a variant of that more common adjective, which ps.-Zonaras (above) has as an epithet of Zeus (the two adjectives would have been homophonous in later Greek).
Adler also compares Lexicon Ambrosianum 430.