Every now and then I find it helpful to look at how words came to be. And if it's not helpful, then at least it's interesting :)

One word whose history fits both, I think, is category.

Its basic roots are Greek: kata meaning generally "down to" and agoreuein or agora. The Greek agora was the market place (or any general assembly). Agoreuein is the verb from agora, and so means "to do something in the marketplace/assembly" - i.e. to speak in public. [An equivalent might be to soapbox: it was a boxy type of noun that people used to stand on (or do in speaker's corner] The agora was a hub of Greek life and it was here that Socrates annoyed people with his questions, doing his agoreuein thing.

When you run these two words - kata and agoreuein- together in Greek you get kategorein. And by mixing this "down" bit with the "do something in public like speaking" you get the a word meaning "to accuse". The noun kategoria means something that was said against someone (normally in a public assembly like a court of law).

Aristotle used the word kategoria in his Categories for his ten classes of things that can be named. And (I'd guess but may be wrong) it is here that we begin to get the classification sense of the word.

I like this accusation bit. It underlines the idea that categorisation is inherently social and negotiated. And that puts a slightly different spin on tagging, for example. When you tag an item, in del.icio.us or whatever, what if you're accusing it of something?

Various things might be said:
- We need to assume that our accusation/tag may be wrong.
- We need to accept that there might be hung juries/ambiguity
- We might be more careful hurling around our accusations/tags
- We accept that things might be unjustly tagged and that their "names need to be cleared".
- We need to accept that other peoples accusations/tags may be right
- We need to understand that different cultures have different norms and so will accuse/tag accordingly
- Del.icio.us is a "cases-pending" clearing house?
- and probably more ...

Of course, times have changed since 300BC, so you might tag this post: idiocy, waste of time, or etymology.