USDA Pomological Watercolors

You meant *keming [1], of course. :)

[1]: https://en.wiktionary.org/wiki/keming

It has nothing to do with this but ok ...

It's technical jargon. Scientists used speak a mishmash of Greek and Latin, since those were common among educated people. That hung on for longer than was realistic, but it became a kind of slang for group recognition.

This department was named in the 1880s. They probably would just call it the Apple Department today, though I admit I still like the tone that sort-of-Greek-or-Latin rings.