Where does “堆積岩” come from?

堆積岩 (Japanese) comes from Japanese 岩, from Old Japanese いわ.

堆積岩 (Japanese): sedimentary rock

Definitions

Step	Language	Word	Meaning
1	Japanese	岩	rock
2	Old Japanese	いわ	—

堆積岩 — Etymology, Origin & Word History | Etymology Explorer