1530s, "attack, assault, a rushing or setting upon," from on + set (n.); compare verbal phrase to set (something) on (someone), c. 1300, originally "sic (a dog) on." Weaker sense of "beginning, start" is recorded from 1560s. Figurative use in reference to a calamity, disease, etc. is from 1580s. Middle English had set (n.3) "attack, onslaught" (mid-14c.).
1660s (trans.), "kindle or set on fire, cause to burn," from Latin ignitus, past participle of ignire "set on fire, make red hot," from ignis "fire" (see igneous). Attested earlier as an adjective (1550s). Intransitive sense of "catch fire, begin to burn" is from 1818. Related: Ignited; igniting.
1590s, "on horseback," past-participle adjective from mount (v.). From 1690s as "set up for display."
1550s, "act of setting off" (on a journey, etc.), from off + set (adj.). Meaning "something 'set off' against something else, a counterbalance" is from 1769; the verb in this sense is from 1792. As a type of printing, in which the inked impression is first made on a rubber roller then transferred to paper, it is recorded from 1906.
c. 1400, appreisen, "to set a value on," from stem of Old French aprisier "appraise, set a price on" (14c., Modern French apprécier), from Late Latin appretiare "value, estimate," from ad "to" (see ad-) + pretium "price" (see price (n.)). The original English spelling, also apprize, was altered by influence of praise. Related: Appraised; appraising.
mid-14c., "make (someone) ardent; set (the spirit, etc.) on fire" with a passion or religious virtue, a figurative sense, from Old French enflamer "catch fire; set on fire" (Modern French enflammer), from Latin inflammare "to set on fire, kindle," figuratively "to rouse, excite," from in- "in" (from PIE root *en "in") + flammare "to flame," from flamma "a flame" (see flame (n.)).
The literal sense of "to cause to burn" first recorded in English late 14c. Meaning "to heat, make hot, cause inflammation" is from 1520s. Formerly also enflame, but since 16c. the spelling with in- has predominated. Related: Inflamed; Inflaming.