NORSE GIANT ETYMOLOGY: Old Norse jötunn (also jǫtunn, see Old Norse orthography) and Old English eoten developed from the Proto-Germanic masculine noun *etunaz. Philologist Vladimir Orel says that semantic connections between *etunaz and Proto-Germanic *etanan make a relation between the two nouns likely. Proto-Germanic *etanan is reconstructed from Old Norse etall “consuming,” Old English etol “voracious, gluttonous,” and Old High German filu-ezzal “greedy.” Old Norse risi and Old High German riso derive from the Proto-Germanic masculine noun *wrisjon. Orel observes that the Old Saxon adjective wrisi-like “enormous” is likely also connected. Old Norse þurs, Old English ðyrs, and Old High German duris “devil, evil spirit” derive from the Proto-Germanic masculine noun *þur(i)saz, itself derived from Proto-Germanic *þurēìnan, which is etymologically connected to Sanskrit turá- “strong, powerful, rich.”

Wikipedia entry for Jötunn