Where does “imperturbable” come from?

imperturbable (Middle French) comes from Late Latin imperturbabilis, from Latin im-, from Latin īn-, from Latin în, from Latin en, from Proto-Italic en, from Proto-Indo-European h₁én — in.

Ancestry of “imperturbable”, step by step

Step	Language	Word	Meaning
1	Late Latin	imperturbabilis	—
2	Latin	im-	Alternative form of in-; form of "in"; in
3	Latin	īn-	un-, non-, not
4	Latin	în	in, at, on, upon, from (space)
5	Latin	en	lookǃ beholdǃ; reallyǃ?; come onǃ
6	Proto-Italic	en	in
7	Proto-Indo-European	h₁én	in

Every word from Proto-Indo-European h₁én →Every word from Latin īn- →Every word from Proto-Italic en →