
English word foss comes from Proto-Indo-European *pers-, and later Proto-Germanic *fursaz (Waterfall, torrent.)
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*pers- (Proto-Indo-European)
*pŕ̥sos (Proto-Indo-European)
*fursaz (Proto-Germanic)
Waterfall, torrent.
foss (Old Norse)
foss (English)
Waterfall (permanent flow of water over the edge of a cliff).