Koko

Koko is a playful, doubled-syllable name that turns up as a real word in more than one context — it's also a regional name for the fast-growing shade tree Albizia lebbeck. It's also familiar from Koko, the western lowland gorilla well known for learning American Sign Language.

The repeated syllable gives it a bouncy, singsong quality that's fun to say and easy for a pet to learn. It suits a curious, expressive companion who always seems to be watching and listening.