Where does “gaisom” come from?

gaisom (Gaulish) comes from Proto-Celtic gaisos, from Proto-Indo-European ǵʰays-, from Proto-Indo-European ǵʰey- — winter.

Ancestry of “gaisom”, step by step

StepLanguageWordMeaning
1Proto-Celticgaisosspear
2Proto-Indo-Europeanǵʰays-pointed stick, spear; spear
3Proto-Indo-Europeanǵʰey-winter
Every word from Proto-Indo-European ǵʰey- →Every word from Proto-Indo-European ǵʰays- →Every word from Proto-Celtic gaisos →