My understanding of the term grub-stake (based on spending too many early teen-age years reading Zane Grey novels - perhaps not the best source) is that it covered not just the food but the tools, tents and other stuff that the prospecters needed. In effect the provider of the stake was investing in the venture and the prospecter (or, disparagingly, grubber)was the one who would be grubbing around for the gold. Hence the grub-stake. Since then its generally accepted application has been restricted to food.