Latin infirmus

← Proto-Indo-European *dʰer- (root)

← Proto-Indo-European *n̥- (inherited)

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

← Proto-Italic *en- (derived)

← Proto-Italic *fermos (inherited)

← Latin in- (affix)

← Latin firmus (affix)

→ English infirm (derived)

→ Romanian infirm (derived)