What is even more curious is the older the earliest reference gets (re Amdur's observation), the more troubling the term becomes as a hybrid reading. . . it seems to me it ought to be a more modern construction . . . The distinctions between appropriate use of foreign and the native sensibilities should be tighter earlier -- and therefore the more unlikely a hybrid reading.
Well, remember that Chinese characters have been in use in Japan since at least the fifth century, and have existed in Japan from Chinese sources from at least the first century. So looking at it from that point of view, the seventeenth century is pretty modern.