Reading Tower of Babel, I made a connection in my head when I came to a mention of Kaferia, homeworld to Tau Cetian insectoids. I've been a longstanding fan of the 1980s RPG 2300AD, set in the year of the title in a human civilization that recovered from global war to starflight and colonization. The major antagonist civilization to the human was that of the Kafers, named such after the German word Käfer meaning "beetle" on account of their insectoid appearance. Given that the natives of Tau Ceti III are insectoid, too, it would seem plausible to assume that the species and their planet acquired their human name via some sort of expedition with at least some speakers of German.
I think you missed the part where I said Kaferia was settled and named by the Kaferi family. Of course, Kaferia is a back-formation from "Kaferian apples" in "Where No Man Has Gone Before." The first mention of Kaferians as insectoid, as far as I know, was 15 years later in the manual accompanying Star Trek Maps. It's possible that the writer of that manual (John Upton, apparently) was aware of the German word and made them insectoid based on that. Although the depiction of them in Shane Johnson's Worlds of the Federation was more antlike than beetle-like.