encyclopedia n.

a Middle English merger of Old English in (prep.) "in, into, upon, on, at, among; about, during;" and Old English inne (adv.) "within, inside," from Proto-Germanic *in (source also of Old Frisian, Dutch, German, Gothic in, Old Norse i), from PIE root *en "in." The simpler form took on both senses in Middle English.

Sense distinction between in and on is from later Middle English, and nuances in use of in and at still distinguish British and American English (in school/at school). Sometimes in Middle English shortened to i.

The noun sense of "influence, access (to power or authorities)," as in have an in with, is first recorded 1929 in American English. to be in for it "certain to meet with something unpleasant" is from 1690s. To be in with "on friendly terms with" is from 1670s. Ins and outs "intricacies, complications of an action or course" is from 1660s. In-and-out (n.) "copulation" is attested from 1610s.

also *kwelə-, Proto-Indo-European root meaning "revolve, move round; sojourn, dwell."

It forms all or part of: accolade; ancillary; atelo-; bazaar; bicycle; bucolic; chakra; chukker; collar; collet; colonial; colony; cult; cultivate; culture; cyclamen; cycle; cyclo-; cyclone; cyclops; decollete; encyclical; encyclopedia; entelechy; epicycle; hauberk; hawse; inquiline; Kultur; lapidocolous; nidicolous; palimpsest; palindrome; palinode; pole (n.2) "ends of Earth's axis;" pulley; rickshaw; talisman; teleology; telic; telophase; telos; torticollis; wheel.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit cakram "circle, wheel," carati "he moves, wanders;" Avestan caraiti "applies himself," c'axra "chariot, wagon;" Greek kyklos "circle, wheel, any circular body, circular motion, cycle of events,"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."