In Latin (and daughter languages), there seems to be a correspondence between nouns of the third declension in -or/-us, -oris denoting a quality, and adjectives of the Ist class in -idus,a,um denoting something or someone possessing the corresponding quality (sometimes approximately, I guess out of semantic drift).
Here are the ones that I could find in Italian (some in Latin). I'm sure there are more, but these are already many enough to suggest a pattern:
CALOR, CALIDUS (Latin)
FRIGUS, FRIGIDUS (Latin)
HUMOR (as in liquid), HUMIDUS (Latin)
AMOR (as in cohesion), AMIDUS (Latin)
timore, timido (Italian)
So, what is the pattern, and how did it originate? Is this appearing also in other IE languages?