Английский Этимологический словарь - will (v.)

- O.E. *willan, wyllan "to wish, desire, want" (past tense wolde), from PIE *wel-/*wol- "be pleasing." The unusual 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.; won't for will not is first recorded mid-15c. as wynnot, later wonnot (1584) before the modern form emerged 1667. Willing is O.E. willendliche.