Proto-Indo-European root meaning "to take, distribute." 

It forms all or part of: assume; consume; emption; example; exemplar; exemplary; exemplify; exempt; exemption; impromptu; peremptory; pre-emption; premium; presume; presumption; prompt; pronto; ransom; redeem; redemption; resume; sample; sejm; subsume; sumptuary; sumptuous; vintage.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit yamati "holds, subdues;" Latin emere "buy," originally "take," sumere "to take, obtain, buy;" Old Church Slavonic imo "to take;" Lithuanian imu, imti "to take."

For the sense shift from "take" to "buy" in the Latin verbs, compare Old English sellan "to give," source of Modern English sell "to give in exchange for money;" Hebrew laqah "he bought," originally "he took;" and colloquial English I'll take it for "I'll buy it." 

also over-sell, 1879, "sell more than one can deliver," from over- + sell (v.). Figurative sense of "make unrealistic or excessive claims for" is by 1928.

also re-sell, "to sell again, sell a second time," 1570s; see re- "back, again" + sell (v.). Related: Resold, reselling.

"merchant, vendor," c. 1200, agent noun from sell (v.). Seller's market, in which demand predominates, is recorded by 1934.

"action of selling," early 14c., verbal noun from sell (v.). Selling-point is attested from 1953 as "retail outlet;" by 1959 as "persuasive fact in a sales pitch."

also sell-out, "corrupt bargain," 1862 (in Mary Chesnut's diary), from the verbal phrase (which from 1796 meant "dispose entirely of one's interests" in a company, etc.); see sell (v.) + out (adv.). Meaning "event for which all tickets have been sold" is attested from 1923. The verbal phrase sell out in the sense of "prostitute one's ideals or talents" is attested from 1888 (selling out).