Yours, Etc.: Origins and Uses of 8 Sign-Offs
c.1400, "made of wood," from stock (n.1). Of plants, "of stout and sturdy growth" (not weedy) it is recorded from 1620s. Of persons, "thick-set," 1670s, suggestive of tree trunks, but cf. also stock in sense of "trunk of the human body" (late 14c.).