c. 1200, aslepe, o slæpe, "in or into a state of slumber," from Old English on slæpe (see a- (1) + sleep (n.)). The parallel form on sleep continued until c. 1550. In religious literature sometimes euphemistic or figurative for "dead" (late 13c.). Meaning "inattentive, off guard" is from mid-14c. In reference to limbs, "numb and having a prickly feeling through stoppage of circulation," from late 14c.
c. 1200, "a falling to the ground; a dropping from a height, a descent from a higher to a lower position (as by gravity); a collapsing of a building," from Proto-Germanic *falliz, from the source of fall (v.). Old English noun fealle meant "snare, trap."
Of the coming of night from 1650s. Meaning "downward direction of a surface" is from 1560s, of a value from 1550s. Theological sense, "a succumbing to sin or temptation" (especially of Adam and Eve) is from early 13c.
The sense of "autumn" (now only in U.S. but formerly common in England) is by 1660s, short for fall of the leaf (1540s). Meaning "cascade, waterfall" is from 1570s (often plural, falls, when the descent is in stages; fall of water is attested from mid-15c.). The wrestling sense is from 1550s. Of a city under siege, etc., 1580s. Fall guy is attested by 1906.
Old English feallan (class VII strong verb; past tense feoll, past participle feallen) "to drop from a height; fail, decay, die," from Proto-Germanic *fallanan (source also of Old Frisian falla, Old Saxon fallan, Dutch vallen, Old Norse falla, Old High German fallan, German fallen, absent in Gothic).
These are from PIE root *pol- "to fall" (source also of Armenian p'ul "downfall," Lithuanian puolu, pulti "to fall," Old Prussian aupallai "finds," literally "falls upon").
The meaning "come suddenly to the ground" is from late Old English. Of darkness, night, from c. 1600; of land sloping from 1570s; of prices from 1570s. Of empires, governments, etc., from c. 1200. Of the face or countenance from late 14c. The meaning "to be reduced" (as temperature) is from 1650s. That of "die in battle" is from 1570s. The meaning "to pass casually (into some condition)" is from early 13c.
To fall in "take place or position" is from 1751. To fall in love is attested from 1520s; to fall asleep is late 14c. (Middle English also used slide asleep, etc.). To fall down is early 13c. (a-dun follon); to fall behind is from 1856. Fall through "fail, come to nothing" is from 1781. To fall for something is from 1903.
To fall out is by mid-13c. in a literal sense; military use is from 1832. The meaning "have a disagreement, begin to quarrel" is attested from 1560s (to fall out with "quarrel with" is from late 15c.).
"be heavy with sleep, be half asleep," 1570s, probably a back-formation from drowsy. Old English had a similar word, but there is a 600-year gap. Related: Drowsed; drowsing.The noun meaning "state of being half asleep" is by 1814.
c. 1300, slepi, "lethargic, weary, overcome with sleep, tending to fall asleep," from sleep (n.) + -y (2). Perhaps from an unrecorded Old English slæpig. Old English did have slæpor, slæpwerig in the sense "sleepy;" slæpnes "sleepiness." Similar formation in Old High German slafag.
It is attested from late 14c. as "inducing sleep." Of places, "quiet, unexciting" from 1813 (Irving's Sleepy Hollow is from 1820). Sleepy-head "idle, lazy person" is from 1570s. Related: Sleepily; sleepiness. Sleepish "somewhat sleepy" is attested from 1520s.
"not asleep, roused from sleep," c. 1300, shortened from awaken, original past participle of Old English awæcnan (see awaken). Figurative use is by 1610s.
"having a tendency to fall or decay," 1797, in botany, from Latin caducus "falling, fallen, fleeting," from cadere "to fall, decline, perish" (from PIE root *kad- "to fall"). Related: Caducity.
"a fall or flow of water over a cliff, a waterfall," 1640s, from French cascade (17c.), from Italian cascata "waterfall," from cascare "to fall," from Vulgar Latin *casicare, frequentative of Latin casum, casus, past participle of cadere "to fall" (from PIE root *kad- "to fall").