Where does “jarn” come from?

jarn (Old Danish) comes from Old Norse járn, from Proto-Germanic īsarną, from Proto-Celtic īsarnom, from Proto-Indo-European h₁ésh₂r̥ — blood.

Ancestry of “jarn”, step by step

Step	Language	Word	Meaning
1	Old Norse	járn	iron
2	Proto-Germanic	īsarną	iron
3	Proto-Celtic	īsarnom	iron
4	Proto-Indo-European	h₁ésh₂r̥	blood

jarn — Etymology, Origin & Word History | Etymology Explorer