"came up short 100 dollars" - what usage of "short" is that?

insufficiency:

short adjective

(3.1) short of/on Not having enough of (something); lacking or deficient in.

the implication is "came up short of money by 100 dollars", but some of the words have been left out.

also "come short" on the same Lexico page

come short

(1) Fail to reach a goal or standard.

so it seems a mixture of "come up" and "come short"

This use of "short" has been described as a "transitive adjective" by Geoff Pullum in the Language Log blog post "New transitive adjectives".

I think the following definition of "to come up" from Merriam-Webster is relevant:

5 : to turn out to be · the coin came up tails

Actually, I think that example isn't a great illustration of the "turn out to be" meaning of "come up", since when talking about a coin the word "up" could be interpreted as referring to the physical orientation of the coin. But MW also lists a idiom that seems similar to the expression used in your sentence:

— come up empty
: to fail to achieve a desired result