fort (n.)youdaoicibaDictYouDict
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, possibly from PIE root *bhergh- (2) "high, elevated," with derivatives referring to hills and hill-forts (see barrow (n.2)). Or possibly from *dher- (2) "to hold firmly, support." Figurative use of hold the fort attested from 1590s.
muscle-man (n.)youdaoicibaDictYouDict
1929, originally "an underworld enforcer;" sense of "strong man" first attested 1952; from muscle (n.) + man (n.).
strong (adj.)youdaoicibaDictYouDict
Old English strang "physically powerful, powerful in effect; forceful, severe, firm, bold, brave; constant, resolute; arduous, violent," from Proto-Germanic *strangaz (cognates: Old Norse strangr "strong," Dutch streng "strict, rigorous," Old High German strang "strong, bold, hard," German streng "strict, rigorous"), possibly from PIE *strenk- "tight, narrow." Originally compared strenger, strengest (compare old/elder/eldest).

Grammatical sense, of noun and verb inflections, is first attested 1841, translating German stark, used in a grammatical sense by J. Grimm (the terms strong and weak better fit German inflections). Strong suit (1865) is from card-playing. Strong man "man of great strength" (especially one who displays it professionally) is recorded from 1690s; meaning "dominating man in a political organization" is from 1859.
Varangian (n.)youdaoicibaDictYouDict
one of the Northmen who ravaged the Baltic coast in 9c. and by tradition overran part of western Russia and founded a dynasty there," 1788, from Medieval Latin Varangus, from Byzantine Greek Barangos, a name ultimately (via Slavic) from Old Norse væringi "a Scandinavian," properly "a confederate," from var- "pledge, faith," related to Old English wær "agreement, treaty, promise," Old High German wara "faithfulness" (see very). Attested in Old Russian as variagi; surviving in Russian varyag "a pedlar," Ukrainian varjah "a big strong man."