I think corda definitely fails to make the grade. Calor is a bit more borderline, but it still seems to be defined only in medical dictionaries, Latin dictionaries, Spanish dictionaries, etc. Rubor seems to be in the same category, and is also not allowed in Chi. The other two related terms, tumor and dolor are alternate spellings of tumour and dolour, and are in our list.
It's true, Dave, that calor has "been around for quite a while" - 1st century, as Binkie informs us. I think that might be part of the problem. Perhaps medicos don't actually use the word these days, since bamboozling the punters with scraps of Latin has gone out of vogue, and heat can be used to convey the same meaning.