early 14c., slippen, "to escape, to move softly and quickly," from an unrecorded Old English word or cognate Middle Low German slippen "to glide, slide," from Proto-Germanic *slipan (source also of Old High German slifan, Middle Dutch slippen, German schleifen "to glide, slide"). This is probably from PIE *sleib-"slip, slide," from root *(s)lei- "slimy, sticky, slippery" (see slime (n.)). The verb is not found in Old English, which did have related adjective slipor "slippery, having a smooth surface." Related: Slipped; slipping. 

It is attested from mid-14c. in the sense of "lose one's footing, slide suddenly and unawares," also "slide out of place," also "fall into error or fault." The meaning "pass unguarded or untaken" is from mid-15c. That of "slide, glide, pass smoothly and easily" is from 1520s.

The transitive sense of "cause to move with a sliding motion" is from 1510s; the meaning "insert surreptitiously, put or place secretly" is from 1680s. The meaning "let loose, release from restraint" (1580s), is probably from the noun sense of "leash for a (hunting) dog that can be easily released" (1570s).

To slip on "put on (clothing, etc.) loosely or in haste" is from 1580s; to slip off "take off noiselessly or hastily" is from 1590s. To slip up "make a mistake, err inadvertently" is from 1855; to slip through the net "evade detection" is by 1829 (for slip through the cracks see crack (n.)). To let (something) slip originally (1520s) was a reference to hounds on a leash; figurative use for "allow to escape through carelessness" is by 1540s.

also land-slide, 1841, "fall or down-slide of a mass of rock, earth, etc. from a slope or mountain," American English, from land (n.) + slide (n.). Earlier was landslip (1670s), which is preferred in Britain. Old English used eorðgebyrst in this sense; literally "earth-burst." Landslide in the political sense "lopsided electoral victory" is attested from 1888.

in the religious sense "abandon faith or devotions, apostatize," 1580s, from back (adv.) + slide (v.). Related: Backslider; backsliding (1550s).

kind of small toboggan, 1905, from French luge "small coasting sled," from Savoy dialect, from Medieval Latin sludia "sled" (9c.), which is perhaps from a Gaulish word from the same root as English sled, slide.

early 14c., sledde, "a dragged vehicle used for transport of heavy goods over hard ground or ice," from Middle Dutch sledde "sled," from Proto-Germanic *slid- (source also of Old Saxon slido, Old Norse sleði, Danish slæde, Swedish släde, Old High German slito, German Schlitten "sledge"), from the same root as Old English slidan (see slide (v.)). Not found in Old English.

In reference to a sleigh used for travel or recreation, it is attested from 1580s, now mainly American English. In reference to a pair of runners connected by a framework with a light platform or seat, used for pleasure coasting, by 1873.

past tense and past participle of slide (v.). An alternative past participle is slidden.

"to slide, slip," from Old English asliderian, from slider "slippery," from the source of slide (v.); also compare slither. Related: Sliddery.

1520s, "one who or that which slides" (in the first attested use, "skater"), agent noun from slide (v.). As a type of terrapin, from 1877; as a type of baseball pitch that seems to drop unexpectedly, 1936.

As "ice cream served as a sandwich between two wafers," by 1915. "Anyone who has felt the ice-cream slipping out of control as it melts will appreciate the name," Ayto writes. It was extended in U.S. to mini-hamburgers-and-buns by 2009: "The concept, of a filling held precariously between two outer layers, is essentially the same" [Ayto].

also slide rule, mathematical calculating tool consisting of two parts, one of which slides along the other, 1660s, from slide (v.) + rule (n.). So called for its method of operation. In early use commonly sliding-rule. Also sometimes sliding-scale (1706), but this has another sense.

early 15c., variant of Middle English slidder "to slip, slide," from Old English slidrian "to slip, slide on a loose slope," a frequentative form of slidan "to slide" (see slide (v.)). For spelling change, compare gather. The specific meaning "walk in a sliding manner" is attested from 1848 in reference to humans. In reference to reptile motion, from 1839. Related: Slithered; slithering.