Where does “甘木” come from?

甘木 (Chinese) comes from Japanese 甘木, from Japanese 木, from Old Japanese 木, from Proto-Japonic kəy — tree.

Ancestry of “甘木”, step by step

Step	Language	Word	Meaning
1	Japanese	甘木	licorice
2	Japanese	木	a tree or shrub; wood, timber, lumber; a tree
3	Old Japanese	木	a tree or shrub; wood, timber, lumber; Combining...
4	Proto-Japonic	kəy	tree