These are some of the words that show up in CCS related to Kero-chan (plus words I use in the site without explaining). I'm sorry these aren't in alphabetical order, but I think they work better organized by category.
Nuigurumi: Is there a more hateful word to Kero-chan's ears? It means stuffed animal/toy.
Fuuin: Seal (not the animal)
Kemono: Monster/beast (So "Fuuin No Kemono" means "Beast of the Seal")
Osaka: Osaka is a Japanese city located near Kyoto. The Clow spent a long time there before ending up in Sakura's basement. You can find it on a map at the Osaka Tourist Guide
Osaka-ben: Dialect of Japanese spoken in Osaka. Kero-chan speaks it, since it rubbed off on him while The Clow was in the region. Osaka-ben has a pretty different sound from standard Japanese (Tokyo-ben is considered "standard Japanese"). I'd say it has a rougher sound and a more "playful" intonation, and it's more casual than standard Japanese. As a result, many anime characters who speak Osaka-ben tend to be either kind of rude, loud, or playful (or all of the above, like Kero-chan). Aya Hisakawa, Kero-chan's seiyuu, was born in Osaka.
Konyanyachiwa:
Osaka-ben for "kon'nichiwa," which is standard Japanese for "hello" or "good afternoon." I've seen it spelled in many different ways, but this is the correct way (
-- I've been asked about this, so I should clarify that this is exactly how it's written in the manga, without the particle 
).
Hona: Osaka-ben for "bye" (literally, it means "anyway"). It's very casual speech, and Kero-chan uses it a lot along with "Hona-na!"
Chau: Osaka-ben for "chigau" ("wrong/different/not"). It's usually repeated, "chau chau." Kero-chan accidentally says this to the little girl that brings him home on ep. 15 (when she says he's a cat), so she calls him "Chauchau," thinking it's his name. ^_^;
Seiyuu: Voice actor/actress. Kero-chan's seiyuu is Aya Hisakawa.
Okashi: Sweets/candy
Keeki: Japanese pronunciation of "cake." Probably Kero-chan's favorite word along with "pudding."
Okonomiyaki: Okonomiyaki, which literally means "grill what you like " (from "konomi" [liking, preference] and "yaku" [to grill/bake]), is a sort of omelet or pancake. You can include your choice of seafood, meats, and vegetables, and it's served with okonomiyaki sauce, mayonnaise, and other things. At okonomiyaki restaurants, you are given the ingredients and you can prepare it on a skillet. Okonomiyaki originated in Osaka, but it's popular all over Japan and has many variations. You can read about okonomiyaki and other Japanese dishes at the The Tokyo Food Page.
Modern-yaki (modan-yaki): A variation of okonomiyaki with eggs and noodles. According to Kero-chan, it's the best kind of okonomiyaki (I concur) and his favorite.
Musume: Kero-chan calls Meiling "musume." It means "daughter" or "young woman." Actually, Kero-chan calls her "ko-musume," which is a pretty rude way to refer to her. Literally, it means "little girl," but as an epithet, its meaning is not quite that cute. ^^;
Gaki: This is what Kero-chan calls Syaoran. It's obviously not a term of endearment, and it means something like "brat."
