well

Noun

Middle English welle, wille "spring of water, pool formed by a spring, pit sunk into the earth to reach water," going back to Old English wælle (Anglian), wiell, wielle (West Saxon, later wille, wylle), going back to a Germanic base *waln(j)- (also *walj-?) with varying stem formations (whence also Old Frisian walla "spring, source," Middle Dutch wal, walle "a seething, boiling heat, spring or river of seething water") and with e-grade ablaut Old High German wella "wave, tide," Old Icelandic vella "boiling, bubbling mass," all nominal derivatives from the base of Germanic *walla- "to well up, seethe, bubble" — more at well entry 2

Note: Comparable nominal formations from Indo-European *u̯el(H)- "seethe, bubble" with zero-grade ablaut are Old Church Slavic vlĭna "wave," Russian volná (< *u̯l̥H-neh₂), Lithuanian vilnìs "wave" (< *u̯l̥H-ni-), Sanskrit ūrmí- "wave" (< *u̯l̥H-mi-).

Verb

Middle English wellen "to rise to the surface, bubble up, boil, seethe," probably in part verbal derivative of welle "spring of water, well entry 1," in part adaptation of the transitive verb wellen "to boil, curdle, melt (metal), refine," going back to Old English wellan, wyllan (< *wiellan) "to cause to boil," probably going back to Germanic *wall(j)an- (whence also Middle Dutch & Middle High German wellen "to make boil," Old Icelandic vella), causative from *wallan- "to well up, seethe, bubble," Class VII strong verb (whence Old English weallan "to boil, bubble up," Old Frisian walla, Old Saxon wallan "to blaze, boil up, well up," Old High German, "to boil up, well up"), a Germanic verbal base of uncertain origin, seen also with a zero-grade present without gemination in Gothic wulan "to seethe, spread (of an ulcer)"

Note: Both the Middle English Dictionary and the Oxford English Dictionary, third edition (OED), treat the two Middle English verbs wellen as simply the same verb; compare, however, J. de Vries (Nederlands Etymologisch Woordenboek), who treats Dutch wellen "to bubble up" (opborrelen) and wellen "to make boil, hammer white-hot metal together" (doen koken, gloeiende metalen aaneenhameren) in separate articles. The OED asserts that there is a range of dialect attestation of the verb (wællan, wellan, willan, wyllan), apparently on the basis of the few forms given in the citations (the imperatives wel, wyl and wæl in recipes): "In Old English the verb shows the expected reflex of the i-mutation of early Old English æ (West Germanic a) before ll, depending on dialect." But if this statement is based on a reconstruction of the immediate pre-Old English form and inflection of the verb, or its West Germanic predecessor, no such reconstruction is given. The etymology itself merely lists a group of supposed Germanic cognates, summarized by the statement "a causative formation < the same Germanic base as wall v.1 [i.e., Old English weallan]." — In addition to *wallan-, Germanic has an apparent e-grade strong verb *wellan-, seen in Old Saxon and Old High German biwellan "to stain, besmirch," Old Icelandic vella "to well over, boil," and probably Old English wollentēar "with streaming tears." Along with a series of nominal formations outside Germanic based on a zero-grade *u̯l̥H- (see note at well entry 1), the Germanic verbs would lead to an Indo-European base *u̯el(H)- "seethe, bubble." Some have seen this etymon as identical with a homonymous base meaning "to roll" (see welter entry 1), the view of H. Rix, et al. (Lexikon der indogermanischen Verben, 2. Auflage, Wiesbaden, 2001). E. Seebold, on the other hand (Vergleichendes und etymologisches Wörterbuch der germanischen starken Verben, Mouton, 1970, p. 552) thinks the connection in sense is not so easily explained ("Wie diese Bedeutungsvielfalt zu erklären ist, bleibt unklar"; likewise Kluge-Seebold, 22. Auflage, s.v. wallen). Seebold points to the proximity of form and identical meaning of Lithuanian vérda, vìrti "to boil, seethe," Old Church Slavic vĭrěti.

Adverb

Middle English wel, going back to Old English, going back to Germanic *welō (whence Old Frisian wol, wel, wal "in a good manner," Old Saxon wola, wela, wala, Old High German wola, Old Norse vel, val), from an adjectival derivative of the base of *weljan- "to want" — more at will entry 1