Where does “septathlon” come from?

septathlon (English) comes from English septa-, from Latin Septem, from Proto-Italic septem, from Proto-Indo-European septḿ̥ — seven.

Ancestry of “septathlon”, step by step

StepLanguageWordMeaning
1Englishsepta-seven
2LatinSeptemseven; 7
3Proto-Italicseptemseven
4Proto-Indo-Europeanseptḿ̥seven
Every word from Proto-Indo-European septḿ̥ →Every word from Proto-Italic septem →Every word from Latin Septem →