Where does “Hidalgo” come from?

Hidalgo (Central Huasteca Nahuatl) comes from Spanish hidalgo, from Old Spanish fidalgo, from Old Spanish fijo, from Latin fīlius, from Old Latin fīlios, from Proto-Indo-European dʰeh₁y-li-os, from Proto-Indo-European dʰeh₁(y)- — to suckle, nurse.