stockyoudaoicibaDictYouDict[stock 词源字典]
stock: [OE] The word stock originally denoted a ‘tree-trunk’. It came from a prehistoric Germanic *stukkaz, which also produced German stock ‘stick’ and Swedish stock ‘log’. The lineal semantic descent to the stocks [14], a punishment device made from large pieces of wood, is clear enough, but how stock came to be used for a ‘supply, store’ (a sense first recorded in the 15th century) is more of a mystery.

It may be that a tradesman’s supply of goods was thought of metaphorically as the trunk of a tree, from which profits grew like branches; and another possibility is that the usage was inspired by an unrecorded application of stock to a wooden storage chest or money box. Stock ‘broth’ was so named (in the 18th century, apparently) because one keeps a ‘stock’ of it on hand in the stockpot, for use at need.

The original notion of a stout piece of wood is preserved in the derivative stocky [14], and also in stock-still [15] – literally ‘as still as a log’.
[stock etymology, stock origin, 英语词源]
stock (n.1)youdaoicibaDictYouDict
Old English stocc "stump, post, stake, tree trunk, log," also "pillory" (usually plural, stocks), from Proto-Germanic *stukkaz "tree trunk" (cognates: 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"), from PIE *(s)teu- (1) "to push, stick, knock, beat" (see steep (adj.)).

Meaning "ancestry, family" (late 14c.) is a figurative use of the "tree trunk" sense (as in family tree). This is also the root of the meaning "heavy part of a tool," and "part of a rifle held against the shoulder" (1540s). Meaning "person as dull and senseless as a block or log" is from c. 1300; hence "a dull recipient of action or notice" (1540s).

Meaning "framework on which a boat was constructed" (early 15c.) led to figurative phrase on stocks "planned and commenced" (1660s). Taking stock "making an inventory" is attested from 1736. Stock, lock, and barrel "the whole of a thing" is recorded from 1817. Stock-still (late 15c.) is literally "as still as a tree trunk."