Etymology

will (v.)
O.E. *willan, wyllan “to wish, desire, want” (past tense wolde), from P.Gmc. *welljan (cf. O.S. willian, O.N. vilja, O.Fris. willa, Du. willen, O.H.G. wellan, Ger. wollen, Goth. wiljan “to will, wish, desire,” Goth. waljan “to choose”), from PIE *wel-/*wol- “be pleasing” (cf. Skt. vrnoti “chooses, prefers,” varyah “to be chosen, eligible, excellent,” varanam “choosing;” Avestan verenav- “to wish, will, choose;” Gk. elpis “hope;” L. volo, velle “to wish, will, desire;” O.C.S. voljo, voliti “to will,” veljo, veleti “to command;” Lith. velyti “to wish, favor,” pa-vel-mi “I will,” viliuos “I hope;” Welsh gwell “better”). Cf. also O.E. wel “well,” lit. “according to one’s wish;” wela “well-being, riches.” The use as a future auxiliary was already developing in O.E. The implication of intention or volition distinguishes it from shall, which expresses or implies obligation or necessity. Contracted forms, especially after pronouns, began to appear 16c., as in sheele for “she will.” The form with an apostrophe is from 17c.
Source: Will (v.). Online Etymology Dictionary. (accessed: October 29, 2006)

Will (1) – Origin: bef. 900; ME willen, OE wyllan; c. D willen, G wollen, ON vilja, Goth wiljan; akin to L velle to wish

Will (2) – Origin: bef. 900; (n.) ME will(e), OE will(a); c. D wil, G Wille, ON vili, Goth wilja; (v.) ME willen, OE willian to wish, desire, deriv. of the n.; akin to will (1)
Source: will. Dictionary.com. Dictionary.com Unabridged (v 1.0.1), Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. (accessed: October 29, 2006).

Will – Middle English willen, to intend to, from Old English willan. See wel-1 in Indo-European Roots.
Source:

Indo-European Roots

ENTRY: wel-1

DEFINITION: To wish, will.

Derivatives include wealth, gallop, gallant, and voluptuous.
1. well-2, from Old English wel, well (< “according to one’s wish”), from Germanic *wel-. 2. weal-1, wealth, from Old English wela, weola, well-being, riches, from Germanic *weln-. 3. will-1, from Old English willa, desire, will power, from Germanic *wiljn-. 4. will-2; nill, willy-nilly, from Old English willan, to desire, from Germanic *wil(l)jan. 5. Germanic compound *wil-kumn- (see gw-). 6. O-grade form *wol-. a. gallop, from Old French galoper, to gallop; b. wallop, from Old North French *waloper, to gallop; c. gallant; gallimaufry, from Old French galer, to rejoice, from Frankish Latin *walre, to take it easy, from Frankish *wala, good, well. a–c all from Germanic *wal-. 7. Basic form *wel-. velleity, volition, voluntary; benevolent, malevolence, from Latin velle (present stem vol-), to wish, will. 8. Probably suffixed extended form *wel-p-i-. voluptuary, voluptuous, from Latin volupts, pleasure, from an adjective *volupis, pleasing (probably preserved in the adverb volup, with pleasure, from neuter *volupe). (Pokorny 2. el- 1137.)
Source: wel-1. Bartleby.com. The American Heritage® Dictionary of the English Language, Fourth Edition. Published by the Houghton Mifflin Company. (accessed: October 29, 2006).