Where does “vicesimus” come from?

vicesimus (Latin) comes from Latin vīgintī, from Latin quīnque, from Proto-Italic kʷenkʷe, from Proto-Indo-European pénkʷe — five.

Ancestry of “vicesimus”, step by step

Step	Language	Word	Meaning
1	Latin	vīgintī	—
2	Latin	quīnque	—
3	Proto-Italic	kʷenkʷe	five
4	Proto-Indo-European	pénkʷe	five

vicesimus — Etymology, Origin & Word History | Etymology Explorer