Where does “causalis” come from?

causalis (Latin) comes from Latin causa, from Old Latin caussa, from Proto-Indo-European kawd-teh₂.

Ancestry of “causalis”, step by step

Step	Language	Word	Meaning
1	Latin	causa	cause, reason; case, claim, contention; motive,...
2	Old Latin	caussa	cause, reason, purpose; case, claim; Archaic form...
3	Proto-Indo-European	kawd-teh₂	—

causalis — Etymology, Origin & Word History | Etymology Explorer