late 14c., spydyr, spither, from earlier spiþre, spiþur, spiþer (mid-14c.), from Old English spiðra, from Proto-Germanic *spin-thron- (cognate with Danish spinder), literally "spinner," from PIE root *(s)pen- "to draw, stretch, spin" + formative or agential *-thro. The connection with the root is more transparent in other Germanic cognates (such as Middle Low German, Middle Dutch, Middle High German, German spinne, Dutch spin "spider").
The male is commonly much smaller than the female, and in impregnating the female runs great risk of being devoured. The difference in sizes is as if the human female should be some 60 or 70 feet tall. [Century Dictionary]
The loss of -n- before spirants is regular in Old English (compare goose (n.), tooth). For shift of -th- to -d- compare murder (n.), burden (n.), rudder.
Not the common word in Old or Middle English, which identified the creatures as loppe (Chaucer's usual word), lobbe. Old English also had atorcoppe (Middle English attercop, literally "poison-head"), and (from Latin aranea), renge; Middle English had araine, "spider," via Old French from the same Latin word; see arachnid). Another Old English word was gangewifre "a weaver as he goes."
In literature, often a figure of cunning, skill, and industry as well as venomous predation; in 17c. English used figuratively for venomousness and thread-spinning but also sensitivity (to vibrations), lurking, independence. As the name for a type of two-pack solitaire, it is attested from 1890, probably based on resemblance of the layout of the decks in the original form of the game (see "Tarbart," "Games of Patience," 1901, p. 49). Spider crab is from 1710, used of various species; spider monkey is from 1764, so called for its long limbs.