grub-stake n.

"larva of an insect," early 15c., perhaps from grub (v.) on the notion of "digging insect," or from the possibly unrelated Middle English grub "dwarfish fellow" (c. 1400). Meaning "dull drudge" is 1650s. The slang sense of "food" is first recorded 1650s, said to be from birds eating grubs, but also often linked with bub "drink."

"that which is placed at hazard as a wager, the sum of money or other valuable consideration which is deposited as a pledge or wager to be lost or won according to the issue of a contest or contingency," 1530s, perhaps from stake (v.2), which is attested a few years earlier, but both the noun and verb are of uncertain origin. Perhaps literally "that which is fixed or put up," either from a particular use of stake (n.1) "stake, pole," or from the notion of "a post on which a gambling wager was placed" (but OED points out there is "no evidence of the existence of such a custom"). Weekley suggests "there is a tinge of the burning or baiting metaphor" in this usage.

Meaning "the prize in a contest of strength, skill, speed, etc." is by 1620s; plural stakes, "sum of money to be won in a (horse) race," is recorded by 1690s (compare sweepstakes). Meaning "an interest, something to gain or lose" is by 1580s; hence have a stake in "have an interest in the turn of events, have something to gain or lose" (1784). The phrase at stake "state of being laid or pledged as a wager; state of being at hazard or in peril" is from c. 1600.