2、来自PIE*kwel, 弯，转。词源同colony, culture, pole.
2、cycle:  Cycle is one of a wide range of English words (including pole, colony, and cult) which go back ultimately to the Indo-European base *qwel-, *qwol-, which signified ‘move around’. Its reduplicated form, *qweqwlo-, produced English wheel, Sanskrit cakrá- ‘wheel, circle’ (ultimate source of the polo term chukker ), and Greek kúklos ‘circle’.English acquired this via French cycle or late Latin cyclus. Its use as a cover term for bicycles, tricycles, etc (of which words in this context it is an abbreviation) dates from the late 19th century. Related forms in English include cyclone ‘mass of rapidly circulating wind’  (probably a modification of Greek kúklōma), cyclamen  (so named from its bulbous roots), and encyclopedia. _ BICYCLE, CHUKKER, COLONY, CULT, ENCYCLOPEDIA, POLE, WHEEL.
4、late 14c., from Late Latin cyclus, from Greek kyklos"circle, wheel, any circular body, circular motion, cycle of events,"from PIE kw(e)-kwl-o-, suffixed, reduplicated form of root *kwel- (1), also *kwele-,"to roll, to move around, wheel"(cognates: Sanskrit cakram"circle, wheel,"carati"he moves, wanders;"Avestan caraiti"applies himself,"c'axra"chariot, wagon;"Greek polos"a round axis"(PIE *kw- becomes Greek p- before some vowels), polein"move around;"Latin colere"to frequent, dwell in, to cultivate, move around,"cultus"tended, cultivated,"hence also"polished,"colonus"husbandman, tenant farmer, settler, colonist;"Lithuanian kelias"a road, a way;"Old Norse hvel, Old English hweol"wheel;"Old Church Slavonic kolo, Old Russian kolo, Polish koło, Russian koleso"a wheel").
6、1842,"revolve in cycles,"from cycle (n.). Meaning"to ride a bicycle"is from 1883. Related: Cycled; cycling.