slot n.1

late 14c., "hollow at the base of the throat above the breastbone," from Old French esclot "hoofprint of a deer or horse," a word of uncertain origin, perhaps from Old Norse sloð "trail" (see sleuth). The anatomical sense is found in romances and in reference to wounds or blows; it is now rare or obsolete. The sense development is obscure, perhaps "from the resemblance of the jugular notch of the sternum to a hoof print" [Middle English Compendium]

The meaning "narrow opening into which something else can be fitted" is by 1520s. The sense of "opening in a machine for a coin to be inserted" is from 1888 (slot machine, one operated by inserting a coin in a slot, is attested by 1891).

The sense of "position in a list, place in a timetable" is attested from 1942. The meaning "middle of the (semi-circular) copy desk at a newspaper," the spot occupied by the chief sub-editor, is recorded from 1917. Slot car is attested by 1966, in reference to the slot in which the miniature car runs.

"bar or bolt used to fasten a shut door, closed window, etc.," early 14c., from Middle Dutch or Middle Low German slot , fr5om Proto-Germanic *slutila- (source also of Old Norse slot, Old High German sluzzil, sloz, German Schloss "bolt, bar, lock, castle;" Old Frisian sletel, Old Saxon slutil "key," Dutch slot "a bolt, lock, castle").

This is from Proto-Germanic *slut- "to close" (source also of Old Frisian sluta, Dutch sluiten, Old High German sliozan, German schliessen "to shut, close, bolt, lock"), thought to be from PIE root *klau- "hook," also "peg, nail, pin," all those things having been used as locks or bolts in primitive structures.

1747, "provide with a slot, cut slots in," from slot (n.1). The meaning "drop a coin in a slot" is from 1888. The figurative sense of "take a position in a particular slot" is from 1940; that of "designate, appoint, fit (something) into a slot" is from 1966. The earliest sense in English is obsolete: "stab in the base of the throat" (c. 1400). Related: Slotted; slotting.

1560s, "to bolt a door," from slot (n.2). Related: Slotted; slotting.