What does "bleed a rock" mean?

Question

In the film McFarland, USA (00:10:08) Principal Camillo says, "I'm supposed to bleed a rock with the budget." What does this mean?

Answer 1

Laurel is correct that this is an allusion to the proverb that “you cannot get blood from a stone.” However, the Cambridge definition provided is very poor—it goes straight to the modern, more metaphorical meaning of the phrase without explaining anything of the history, or the more literal meaning.

On a quick web search, I like this explanation from the Phrase Finder best:

You cannot extract what isn't there to begin with.

Stones don’t have blood, so no matter what you do, you’re not going to get blood out of them. It isn’t a question of your technique or how hard you try, because it is literally impossible. If it actually happened, it would constitute a miracle—only divine intervention could make such a thing possible. The image of a bleeding stone feels very similar to various Biblical miracles, so the possibility of divine intervention is very much a part of the proverb—to emphasize the impossibility of the activity otherwise.

The Phrase Finder cites a 1788 source, Winter Evenings by Vicesimus Knox, referring to this phrase as “that common observation.” They then go on to suggest that the phrase entered the English language via Italian, though they don’t dig into its Italian history prior to that. (The Phrase Finder also discusses “the variant of this proverb that is best known in the USA,” where we’re talking about a turnip rather than a stone—as an American, gotta say, I’ve never heard that before in my life, it’s always from a stone.)

Anyway, point is, in its closer-to-literal sense, “you cannot get blood from a stone” means your “stone” doesn’t have the “blood” to give. The phrase is often used in this sense even today—it brings to mind a lawsuit against someone who has gone bankrupt, pointing out that even if you win the suit, you still aren’t going to get any money because the money doesn’t exist to get.

The more-metaphorical usage is a form of hyperbole—it’s not literally impossible to get the “blood” from the “stone,” and the phrase is being used to highlight the difficulty of it. This kind of hyperbole is used to blur the line here: it is a claim that, despite the apparent existence of the “blood” to get, it is still actually impossible to get it.

The case in the question is an excellent example of this: the budget isn’t actually zero, so there are some funds with which to perform the tasks. It just isn’t enough. The speaker is claiming that, at some point, the funds are going to run out, and there is no way all the required tasks will be funded. At that point, there won’t be any “blood” (money) in the “stone” (budget), and it won’t be possible to get more. The speaker is claiming that reaching that point is literally unavoidable—again, perhaps barring divine intervention.

Answer 2

This is playing off the meaning of the idiom "get blood out of/from a stone":

to make someone give or tell you something, when it is extremely difficult because of the character or mood of the person or organization you are dealing with — Cambridge

It means that the budget is very tight, but the principal is still expected to essentially perform a miracle in order so the school has the personnel, supplies, and services necessary to operate.

Answer 3

You can't bleed a rock, because, being a rock, there is no blood in it.

Thus, the metaphor is that the people who created the budget want the impossible.