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actual (adj.)[actual 词源字典]: early 14c., "pertaining to an action," from Old French actuel "now existing, up to date" (13c.), from Late Latin actualis "active, pertaining to action," adjectival form of Latin actus (see act (n.)). The broader sense of "real, existing" (as opposed to potential, ideal, etc.) is from late 14c.[actual etymology, actual origin, 英语词源]
actuality (n.): late 14c., "power, efficacy," from Old French actualite and directly from Medieval Latin actualitatem (nominative actualitas), from Late Latin actualis (see actual). A Latin loan-translation of Greek energeia. Meaning "state of being real" is from 1670s (actualities "existing conditions" is from 1660s).
Mod. use of actuality in the sense of realism, contact with the contemporary, is due to Fr. actualité, from actuel, which does not mean actual, real, but now existing, up to date. [Weekley]
dap (n.): fist-bump greeting, with various theories as to origin and name meaning. In U.S. popular black culture by 1972 and controversial during the Vietnam War when used by U.S. soldiers, as it often was regarded by whites as a ritual act of black solidarity. Probably imitative (dap was used in 19c. for the bounce of a ball or the skip of a stone on water). Dap, meanwhile, is listed in the DAS as black slang c. 1950 for "aware, up to date," also "stylish, well-dressed," in the latter case at least a shortening of dapper.
fat (adj.): Old English fætt "fat, fatted, plump, obese," originally a contracted past participle of fættian "to cram, stuff," from Proto-Germanic *faitida "fatted," from verb *faitjan "to fatten," from *faita- "plump, fat" (cognates: Old Frisian fatt, Old Norse feitr, Dutch vet, German feist "fat"), from PIE *poid- "to abound in water, milk, fat, etc." (source also of Greek piduein "to gush forth"), from root *peie- "to be fat, swell" (cognates: Sanskrit payate "swells, exuberates," pituh "juice, sap, resin;" Lithuanian pienas "milk;" Greek pion "fat; wealthy;" Latin pinguis "fat").

Meaning "abounding in comforts, prosperous" is late 14c. Teen slang meaning "attractive, up to date" (also later phat) is attested from 1951. Fat cat "privileged and rich person" is from 1928; fat chance "no chance at all" attested from 1905, perhaps ironic (the expression is found earlier in the sense "good opportunity"). Fathead is from 1842; fat-witted is from 1590s; fatso is first recorded 1943. Expression the fat is in the fire originally meant "the plan has failed" (1560s).
modern (n.): 1580s, "person of the present time" (contrasted to ancient, from modern (adj.). From 1897 as "one who is up to date."
modification (n.): c. 1500, in philosophy, from Middle French modification (14c.) and directly from Latin modificationem (nominative modificatio) "a measuring," noun of action from past participle stem of modificare (see modify). Meaning "alteration to an object to bring it up to date" is from 1774. Biological sense is attested by 1896.
now (adv.): Old English nu "now, at present, immediately; now that," also used as an interjection and as an introductory word; common Germanic (Old Norse nu, Dutch nu, Old Frisian nu, German nun, Gothic nu "now"), from PIE *nu "now" (cognates: Sanskrit and Avestan nu, Old Persian nuram, Hittite nuwa, Greek nu, nun, Latin nunc, Old Church Slavonic nyne, Lithuanian nu, Old Irish nu-). Perhaps originally "newly, recently," and related to the root of new.

Often merely emphatic; non-temporal usage (as in Now, then) was in Old English. The adjective meaning "up to date" first recorded 1967, but the word was used also as an adjective in Middle English with the sense "current" from late 14c. Now and then "occasionally" is from 1530s; now or never attested from 1550s.
up-to-date (adv.): 1840, "right to the present time," from phrase up to date, probably originally from bookkeeping. As an adjective from 1865. Meaning "having the latest facts" is recorded from 1889; that of "having current styles and tastes" is from 1891.