Welsh neidr

← Breton naer (cognate)

← Proto-Celtic *natrixs (inherited)

← Welsh nyddu (mention)

← Welsh noden (mention)

← Welsh nodwydd (mention)

← English adder (cognate)

← Irish nathair (cognate)

← Proto-Indo-European *nh₁trih₂ (inherited)

← Proto-Indo-European *snéh₁- (mention)

← Latin natrīx (cognate)

→ English adder (cognate)

→ Breton naer (cognate)

→ Welsh nadroedd (affix)

→ Irish nathair (cognate)

→ Scottish Gaelic nathair (cognate)