Seethe comes from Old English 'sēothan' ('to boil'), from Proto-Germanic *seuthaną, from Proto-Indo-European *seut- ('to boil, seethe'). The historical chain includes Old English sēothan, Proto-Germanic *seuthaną, and Proto-Indo-European *seut-. The quoted older senses, "sēothan", "to boil", and "to boil, seethe", supply the semantic anchors for seethe. The formation is best read as borrowed: the word seethe carries its older form-history into a compact English lexical shape. In present English it is used as a verb, "to be filled with intense but unexpressed anger, or to boil and bubble". English derivatives include seething; related English forms include sodden and sod. The result is a verb whose etymology preserves both the older form and the later English specialization.