I realize that the English word "umbrella" smells like a diminutive of umbra, "shadow". However, all mentions of an "umbrella" from ancient Rome or Greece I have found concern protection from the Sun, whereas I am interested in umbrellas as a means of protection against rain. (This may have something to do with my being now in Cambridge rather than Texas.) It appears that this kind of umbrella against rain was not known in ancient Rome — do correct me if I'm wrong.
What would be a good Latin word for an umbrella? There is no need for it to be classical (unless there is good classical precedent, of course), I just want a useful word for present day. An attested phrase would be great, but other kinds of suggestions are also welcome. I have posted one possibility below, but I'm sure there are other ones, or at least better reasoning for mine.