Proto-IE: *sret- (-th-)
Meaning: to be rough (ab. the sea), to seethe
Old Greek: rhótho-s m. `das Rauschen der Wogen, der Ruder'
Latin: fretum, -ī n., fretus, -ūs m. `Brandung, Wallung des Meeres; Meerenge, Sund'
Celtic: *sret- > MIr srithide fola `Ströme Blutes'; OCorn (gl.) stret `latex', MCorn streyth `Fluss'
Russ. meaning: ходить (о волнах на море), бурлить etc.
References: WP II 704 (different in Pok.)