stocking (n.)

Middle English stok, from Old English stocc "stump, wooden post, stake; trunk of a living tree; log," also "pillory" (usually plural, stocks), from Proto-Germanic *stauk- "tree trunk" (source also of Old Norse stokkr "block of wood, trunk of a tree," Old Saxon, Old Frisian stok, Middle Dutch stoc "tree trunk, stump," Dutch stok "stick, cane," Old High German stoc "tree trunk, stick," German Stock "stick, cane;" also Dutch stuk, German Stück "piece").

This is said to be from an extended form of PIE root *(s)teu- (1) "to push, stick, knock, beat" (see steep (adj.)), but Boutkan considers that instead it is "probably" from an extended form of the root *sta- "to stand, make or be firm."

In old use often paired alliteratively with stone (n.). With specific technical senses based on the idea of "principal supporting part" of a tool or weapon (to which others were affixed), such as "block from which a bell is hung," "gun carriage" (both late 15c.).

The sense of "part of a rifle held against the shoulder" is from 1540s. Stock, lock, and barrel "the whole of a thing" is recorded from 1817.

The meaning "line of descent, ancestry" is from late 12c.; that of "original progenitor of a family" is late 14c.; figurative uses of the "trunk of a living tree" sense (compare the notion in family tree and the family sense of stem (n.)). 

In comparisons, the meaning "person as dull and senseless as a block or log" is from c. 1300; hence "a dull recipient of action or notice" (1510s), as in laughing-stock and compare butt (n.3).

also blue-stocking, 1790, derisive word for a woman considered too learned; see blue (adj.1) + stocking. The usage traces to a London literary salon founded c. 1750 by Elizabeth Montagu on the Parisian model, featuring intellectual discussion instead of card games and in place of ostentatious evening attire simple dress, including notably Benjamin Stillingfleet's blue-gray tradesman's hose, which he wore in place of gentleman's black silk. Hence the term, first applied in derision to the whole set by Admiral Boscawen. None of the ladies wore blue stockings. The phrase was borrowed by the neighbors in loan-translations such as French bas-bleu, Dutch blauwkous, German Blaustrumpf.