Where does “iarnaigh” come from?

iarnaigh (Irish) comes from Irish iarann, from Old Irish íarn, from Proto-Celtic īsarnom, from Proto-Indo-European h₁ésh₂r̥ — blood.

iarnaigh (Irish): to put in irons; to fit, cover with iron;...

Definitions

Step	Language	Word	Meaning
1	Irish	iarann	iron
2	Old Irish	íarn	iron
3	Proto-Celtic	īsarnom	iron
4	Proto-Indo-European	h₁ésh₂r̥	blood

iarnaigh — Etymology, Origin & Word History | Etymology Explorer