Where does “ombro” come from?

ombro (Old Portuguese) comes from Latin umerus, from Proto-Indo-European h₃émsos — shoulder.

Ancestry of “ombro”, step by step

Step	Language	Word	Meaning
1	Latin	umerus	the humerus bone; shoulder; back, ridge, such as...
2	Proto-Indo-European	h₃émsos	shoulder