Where does “Kawaguchi” come from?

Kawaguchi (English) comes from Japanese 川口, from Japanese 口, from Japanese くち, from Japanese 朽ちる.

Ancestry of “Kawaguchi”, step by step

Step	Language	Word	Meaning
1	Japanese	川口	mouth of river, estuary
2	Japanese	口	mouth; opening; the mouth
3	Japanese	くち	mouth
4	Japanese	朽ちる	—