Where does “fīliālis” come from?

fīliālis (Latin) comes from Latin fīlius, from Old Latin fīlios, from Proto-Indo-European dʰeh₁y-li-os, from Proto-Indo-European dʰeh₁(y)- — to suckle, nurse.

Ancestry of “fīliālis”, step by step

Step	Language	Word	Meaning
1	Latin	fīlius	—
2	Old Latin	fīlios	—
3	Proto-Indo-European	dʰeh₁y-li-os	sucker
4	Proto-Indo-European	dʰeh₁(y)-	to suckle, nurse

Every word from Proto-Indo-European dʰeh₁(y)- →

fīliālis — Etymology, Origin & Word History | Etymology Explorer