Where does “Γουλιέλμος” come from?

Γουλιέλμος (Greek) comes from Medieval Latin Gulielmus, from Proto-Germanic Wiljahelmaz, from Proto-Germanic helmaz, from Proto-Germanic halmaz, from Proto-Indo-European ḱolh₂mos, from Proto-Indo-European ḱelh₂- — to pierce, strike; to stick; prick; stab.

Ancestry of “Γουλιέλμος”, step by step

StepLanguageWordMeaning
1Medieval LatinGulielmus—
2Proto-GermanicWiljahelmaz—
3Proto-Germanichelmazhelmet
4Proto-Germanichalmazhalm; stem; stalk; straw; hay
5Proto-Indo-Europeanḱolh₂mosstalk
6Proto-Indo-Europeanḱelh₂-to pierce, strike; to stick; prick; stab
Every word from Proto-Indo-European ḱelh₂- →Every word from Proto-Indo-European ḱolh₂mos →Every word from Proto-Germanic halmaz →