Old English fleon, flion "take flight, fly from, avoid, escape" (contracted class II strong verb; past tense fleah, past participle flogen), from Proto-Germanic *fleuhanan "to run away" (source also of Old High German fliohan, Old Norse flöja, Old Frisian flia, Dutch vlieden, German fliehen, Gothic þliuhan "to flee"), probably from PIE *pleuk-, extended form of root *pleu- "to flow," but Boutkan is not convinced. Also compare fly (v.2).
Weak past tense and past participle fled emerged in Middle English under influence of Scandinavian. Old English had a transitive form, geflieman "put to flight, banish, drive away," which came in handy in the Anglo-Saxon Chronicle. Related: fled; Fleeing.
1570s, from French subterfuge (14c.) or directly from Medieval Latin subterfugium "an evasion," from Latin subterfugere "to evade, escape, flee by stealth," from subter "beneath, below;" in compounds "secretly" (from PIE *sup-ter-, suffixed (comparative) form of *(s)up-; see sub-) + fugere "flee" (see fugitive (adj.)).
late 14c., "fleeing, having fled, having taken flight," from Old French fugitif, fuitif "absent, missing," from Latin fugitivus "fleeing," past-participle adjective from stem of fugere "to flee, fly, take flight, run away; become a fugitive, leave the country, go into exile; pass quickly; vanish, disappear, perish; avoid, shun; escape the notice of, be unknown to," from PIE root *bheug- "to flee" (source also of Greek pheugein "to flee, escape, go into exile, be on the run," phyza "(wild) flight, panic," phyge "flight, exile;" Lithuanian būgstu, būgti "be frightened," bauginti "frighten someone," baugus "timid, nervous;" perhaps also Avestan būj(i)- "penance, atonement," būjat "frees"). Old English had flyma.
Meaning "lasting but a short time, fleeting" is from c. 1500. Hence its use in literature for short compositions written for passing occasions or purposes (1766).
"shelter or protection from danger, assistance in distress," late 14c., from Old French refuge "hiding place" (12c.), from Latin refugium "a taking refuge; a place of refuge, place to flee back to," from re- "back" (see re-) + fugere "to flee" (see fugitive (adj.)) + -ium neuter suffix in a sense of "place for."
By late 19c. especially "temporary shelter for the destitute or homeless." To take refuge "seek safety or shelter (in)," literally or figuratively, is by 1690s.