Where does “kahdeksankymmenvuotias” come from?

kahdeksankymmenvuotias (Finnish) comes from Finnish kahdeksan, from Proto-Finnic kakteksa, from Proto-Finnic kakci, from Proto-Uralic *kakta.

Ancestry of “kahdeksankymmenvuotias”, step by step

kahdeksankymmenvuotias traces back through two separate lines of ancestry.

via Finnish kahdeksan

StepLanguageWordMeaning
1Finnishkahdeksaneight
2Proto-Finnickakteksaeight
3Proto-Finnickakcitwo
4Proto-Uralic*kakta—

via Finnish kymmen

StepLanguageWordMeaning
1Finnishkymmenten; decade
2Proto-Finnickümmenten; decade, group of ten
Every word from Proto-Uralic *kakta →Every word from Proto-Finnic kakci →Every word from Proto-Finnic kakteksa →