Where does “decimal” come from?

decimal (Portuguese) comes from Latin decimalis, from French décimal, from Medieval Latin decimalis, from Latin Decimus, from Latin decem, from Latin -nus, from Proto-Italic -nos, from Proto-Indo-European -nós — Creates verbal adjectives from roots.

decimal (Portuguese): decimal concerning numbers expressed in decimal or calculations using decimal

Definitions

decimal concerning numbers expressed in decimal or calculations using decimal

Ancestry of “decimal”, step by step

Step	Language	Word	Meaning
1	Latin	decimalis	decimal
2	French	décimal	decimal
3	Medieval Latin	decimalis	—
4	Latin	Decimus	originally used for a tenth-born son
5	Latin	decem	ten; 10
6	Latin	-nus	-an
7	Proto-Italic	-nos	Creates verbal adjectives from verb stems
8	Proto-Indo-European	-nós	Creates verbal adjectives from roots

Every word from Proto-Indo-European -nós →Every word from Latin -nus →Every word from Latin decem →