Where does “Porto” come from?

Porto (Old Portuguese) comes from Latin Portus (Cale), from Latin portus, from Proto-Italic portus, from Proto-Indo-European pértus, from Proto-Indo-European per-, from Proto-Indo-European pr̥tós — passed , crossed.

Ancestry of “Porto”, step by step

Step	Language	Word	Meaning
1	Latin	Portus (Cale)	—
2	Latin	portus	harbour, port; haven, refuge, asylum, retreat;...
3	Proto-Italic	portus	harbour
4	Proto-Indo-European	pértus	crossing
5	Proto-Indo-European	per-	before, in front; first; to go through
6	Proto-Indo-European	pr̥tós	passed , crossed

Every word from Proto-Indo-European pr̥tós →Every word from Proto-Indo-European per- →Every word from Proto-Indo-European pértus →