O.E.
hwile, acc. of
hwil "a space of time," from P.Gmc.
*khwilo (cf. O.S.
hwil, O.Fris.
hwile, O.H.G.
hwila, Ger.
Weile, Goth.
hveila "space of time, while"), originally "rest" (cf. O.N.
hvila "bed,"
hvild "rest"), from PIE
*qwi- "rest" (cf. Avestan
shaitish "joy," O.Pers.
šiyatish "joy," L.
quies "rest, repose, quiet," O.C.S.
po-koji "rest"). Notion of "period of rest" became in Gmc. "period of time." Now largely superseded by
time except in formulaic constructions (e.g.
all the while). M.E. sense of "time spent in doing something" now only preserved in
worthwhile and phrases such as
worth (one's) while. As a conjunction (late O.E.), it represents O.E.
þa hwile þe; form
whiles is recorded from c.1220;
whilst is from c.1375, with excrescent
-st as in
amongst,
amidst (see
amid).
[hwahyl, wahyl] 
noun, conjunction, preposition, verb, whiled, whil⋅ing.