Other forms: seething, seethes, seethed
To seethe is to boil — or to be filled with rage you are not letting out. Both meanings turn on the same picture.
The literal sense is old and mostly gone, surviving in seething water and in the noun seething mass. The living use is about anger, and somebody seething is furious and silent, which is exactly what makes it worse. It takes with. There is a third sense about crowds, since a street seething with people is packed and moving. The adjective seething works for all three.
To seethe is to boil. Old English sēoþan meant to boil or to cook, so somebody seething with anger is a pot held just under the boil.
Proto-Indo-European
*h₂sewt-
Proto-Germanic
*seuþaną — to boil, seethe
Proto-West Germanic
*seuþan
Old English
sēoþan — to boil, seethe; to cook; etc.
Middle English
sethen
English, today
seethe
Built from
The verb is derived from Middle English sethen, seeth (“to boil, seethe; to cook; etc.”)cethen, cethyn, sede, seden, seethe, seith, seithe, seth, sethe, sethene, syede, sith, sithe, sithen, zeoth, zeothen, zeotheon, (chiefly Early Middle English) seþe, seþen, seoth, seothe, seothen, seoþe, seoþen, (Early Middle English) seit, seod, soð, from Old English sēoþan (“to boil, seethe; to cook; etc.”), from Proto-West Germanic seuþan, from Proto-Germanic seuþaną (“to boil, seethe”), from Proto-Indo-European h₂sewt-, h₂sew-, h₂sut- (“to move about, roil, seethe”). The noun is derived from the verb. 2
Etymology from Wiktionary, CC BY-SA