Where does “3o” come from?

3o (Spanish) comes from Spanish tercero, from Latin tertiārius, from Latin tertius, from Latin trēs, from Proto-Italic trēs, from Proto-Indo-European *tréyes.

3o (Spanish): Alternative form of 3º

Definitions

Alternative form of 3º

Ancestry of “3o”, step by step

Step	Language	Word	Meaning
1	Spanish	tercero	third; third party; mediator
2	Latin	tertiārius	containing a third part
3	Latin	tertius	third, the ordinal number after secundus and...
4	Latin	trēs	three; 3
5	Proto-Italic	trēs	three
6	Proto-Indo-European	*tréyes	—

Every word from Proto-Indo-European *tréyes →Every word from Proto-Italic trēs →Every word from Latin trēs →