French dur

← Proto-Indo-European *deru- (derived)

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

← Latin dūrus (inherited)

→ English dour (cognate)

→ French ferme (link)

→ French durissime (suffix)

→ French dureté (affix)

→ French endurcir (confix)

→ French durillon (suffix)

→ Romanian dur (borrowed)