Where does “丹誠” come from?

丹誠 (Japanese) comes from Japanese 丹, from Old Japanese 丹.

丹誠 (Japanese): Alternative form of 丹精

Definitions

Step	Language	Word	Meaning
1	Japanese	丹	the color red; red earth; cinnabar
2	Old Japanese	丹	—

丹誠 — Etymology, Origin & Word History | Etymology Explorer