Where does “issei” come from?

issei (English) comes from Japanese 一世, from Japanese 一, from Japanese 始め, from Japanese 始める — begin; start; initiate; originate.

issei (English): A member of the first generation of Japanese...

Definitions

Step	Language	Word	Meaning
1	Japanese	一世	first generation
2	Japanese	一	one, 1; "term relating to the number one"; unity
3	Japanese	始め	beginning, the start of an activity or time...
4	Japanese	始める	begin; start; initiate; originate