Where does “colo” come from?

colo (Old Portuguese) comes from Latin collum, from Latin -is, from Latin -a, from Proto-Italic -ā, from Proto-Indo-European -éh₂.

Ancestry of “colo”, step by step

Step	Language	Word	Meaning
1	Latin	collum	neck, throat; upper stem of a plant; servitude
2	Latin	-is	suffixed to the root of nouns in composition,...
3	Latin	-a	suffixed to the roots of verbs, forms agent...
4	Proto-Italic	-ā	Forms masculine agent nouns from prefixed or compounded bases
5	Proto-Indo-European	-éh₂	—