mid-15c., "fortified place, stronghold," from Old French fort "fort, fortress; strong man," noun use of adjective meaning "strong, stout, sturdy; hard, severe, difficult; hard to understand; dreadful, terrible; fortified" (10c.), from Latin fortis "strong, mighty; firm, steadfast; brave, spirited," from Old Latin forctus, which is of unknown etymology. Possibly from PIE root *bhergh- (2) "high, elevated," with derivatives referring to hills and hill-forts, or possibly from *dher- "to hold firmly, support." Figurative use of hold the fort attested from 1590s.

"that which is up," 1530s, from up (adv.). Phrase on the up-(and-up) "honest, straightforward" first attested 1863, American English.

military installation in South Carolina, U.S., begun in 1827, named for U.S. Revolutionary War officer and Congressman Thomas Sumter (1734-1832), "The Carolina Gamecock." The family name is attested from 1206, from Old French sommetier "driver of a pack horse" (see sumpter). The U.S. Civil War is held to have begun with the firing of rebel batteries on the government-held fort on April 12, 1861.

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.

prefix with various senses, from Old English up (adv.), corresponding to similar prefixes in other Germanic languages.

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).

c. 1300, "dwelling inland or upland," from up (adv.). Meaning "going up" is from 1784. From 1815 as "excited, exhilarated, happy," hence "enthusiastic, optimistic." Up-and-coming "promising" is from 1848. Musical up-tempo (adj.) is recorded from 1948.

also markup, "amount added by a retailer to cover overhead and provide profit," 1899, from the verbal phrase in this sense (by 1870); see mark (v.) + up (adv.).

"advance toward maturity," 1530s, from grow (v.) + up (adv.). As a command to be sensible, from 1951.

c. 1300, "suspend (something) so that it is supported only from above;" see hang (v.) + up (adv.); telephone sense by 1911. The noun hang-up "psychological fixation" is first attested 1959, from notion of being suspended in one place.