A colleague asked me this question, and I couldn't come up with an answer that satisfied him, so I'm wondering if anyone can help:
Why does a man with a short temper become a short-tempered man?
In other words, why do you need the -ed at the end?
Are there any special rules for this?
Best Answer
This must not be taken as a definitive answer. Only hints too long to fit in a comment.
A - In order to form a compound adjective of the type adj+noun-ed, I'd say:
1- the noun should be able to transform into a reasonably comprehensible ed-adjective
2- the adjective in the first part of the compound word must fit with the noun-ed adjective.
B- I've just gone back to an academic paper I'd read a while ago exploring compound adjectives and in particular "the noun + -ed structure".
Here's a paragraph from this paper, it doesn't really answer the "why" in your question, but points toward a possible answer. (Paper's in French, translation mine).
Further on in this paper the author compares the compound noun "middle-age" to the adjective "middle-aged". Could we imagine short-temper as a possible noun? Then could we say the -ed suffix differentiates the noun from the adjective?
A question with/without “-ed” for the compound adjectives formed by “adj.+noun”? had been asked on english.se, and thanks to FumbleFingers for pointing out to John Lawler's comment on the disappearance of "ed" in spoken (and consequently written form) English.