elementary intransitive verb of motion, Old English cuman "to move with the purpose of reaching, or so as to reach, some point; to arrive by movement or progression;" also "move into view, appear, become perceptible; come to oneself, recover; arrive; assemble" (class IV strong verb; past tense cuom, com, past participle cumen), from Proto-Germanic *kwem- (source also of Old Saxon cuman, Old Frisian kuma, Middle Dutch comen, Dutch komen, Old High German queman, German kommen, Old Norse koma, Gothic qiman), from PIE root *gwa- "to go, come."
The substitution of Middle English -o- for Old English -u- before -m-, -n-, or -r- was a scribal habit before minims to avoid misreading the letters in the old style handwriting, which jammed them together. The practice similarly transformed some, monk, tongue, worm. Modern past tense form came is Middle English, probably from Old Norse kvam, replacing Old English cuom.
Meaning "to happen, occur" is from early 12c. (come to pass "happen, occur" is from 1520s). As an invitation to action, c. 1300; as a call or appeal to a person (often in expanded forms: "come, come," "come, now"), mid-14c. Come again? as an off-hand way of asking "what did you say?" is attested by 1884. For sexual senses, see cum.
Remarkably productive with prepositions (NTC's "Dictionary of Phrasal Verbs" lists 198 combinations); consider the varied senses in come to "regain consciousness," come over "possess" (as an emotion), come at "attack," come on (interj.) "be serious," and come off "occur, have some level of success" (1864). Among other common expressions are:
To come down with "become ill with" (a disease), 1895; come in, of a radio operator, "begin speaking," 1958; come on "advance in growth or development," c. 1600; come out, of a young woman, "make a formal entry into society," 1782; come round "return to a normal state or better condition," 1841; come through "act as desired or expected," 1914; come up "arise as a subject of attention," 1844; come up with "produce, present," 1934.
To have it coming "deserve what one suffers" is from 1904. To come right down to it "get to fundamental facts" is from 1875.
Old English up, uppe, from Proto-Germanic *upp- "up" (source also of Old Frisian, Old Saxon up "up, upward," Old Norse upp; Danish, Dutch op; Old High German uf, German auf "up"; Gothic iup "up, upward," uf "on, upon, under;" Old High German oba, German ob "over, above, on, upon"), from PIE root *upo "under," also "up from under," hence also "over."
As a preposition, "to a higher place" from c. 1500; also "along, through" (1510s), "toward" (1590s). Often used elliptically for go up, come up, rise up, etc. Up the river "in jail" first recorded 1891, originally in reference to Sing Sing, which is up the Hudson from New York City. To drive someone up the wall (1951) is from the notion of the behavior of lunatics or caged animals. Insulting retort up yours (scil. ass) is attested by late 19c.
1550s, "to drive and catch (swans)," from up (adv.). Intransitive meaning "get up, rise to one's feet" (as in up and leave) is recorded from 1640s. Sense of "to move upward" is recorded from 1737. Meaning "increase" (as in up the price of oil) is attested from 1915. Compare Old English verb uppian "to rise up, swell." Related: Upped; upping. Upping block, used for mounting or dismounting horses, carriages, etc., is attested from 1796 (earlier was horsing-block, 1660s).