1590s, "to identify by an earmark," from earmark (n.). Meaning "to set aside money for a special purpose" is attested by 1868. Related: Earmarked; earmarking.
Old English earnian "deserve, earn, merit, labor for, win, get a reward for labor," from Proto-Germanic *aznon "do harvest work, serve" (source also of Old Frisian esna "reward, pay"), denominative verb from *azno "labor" especially "field labor" (source of Old Norse önn "work in the field," Old High German arnon "to reap"), from PIE root *es-en- "harvest, fall" (source also of Old High German aren "harvest, crop," German Ernte "harvest," Old English ern "harvest," Gothic asans "harvest, summer," Old Church Slavonic jeseni, Russian osen, Old Prussian assanis "autumn"). Also from the same root are Gothic asneis, Old High German esni "hired laborer, day laborer," Old English esne "serf, laborer, man." Related: Earned; earning.
"one who earns," in any sense, 1610s, agent noun from earn.
"serious or grave in speech or action," early 14c., ernest, from Old English eornoste (adj.) "zealous, serious," or from Old English noun eornost "seriousness, serious intent" (surviving only in the phrase in earnest), from Proto-Germanic *er-n-os-ti- (source also of Old Saxon ernust, Old Frisian ernst, Old High German arnust "seriousness, firmness, struggle," German Ernst "seriousness;" Gothic arniba "safely, securely;" Old Norse ern "able, vigorous," jarna "fight, combat"), perhaps from PIE root *er- (1) "to move, set in motion." The proper name Ernest (literally "resolute") is from the same root. Related: Earnestness.
"portion of something given or done in advance as a pledge," early 15c., with unetymological -t- (perhaps from influence of the other earnest), from Middle English ernes (c. 1200), "a pledge or promise;" often "a foretaste of what is to follow;" also (early 13c.) "sum of money as a pledge to secure a purchase or bind a bargain (earnest-money); from Old French erres and directly from Latin arra, probably from Phoenician or another Semitic language (compare Hebrew 'eravon "a pledge"). Sometimes in Middle English as erness, suggesting it was perceived as er "early" + -ness.