Welsh llau

← Breton laou (cognate)

← Proto-Celtic *luwā (inherited)

← English louse (cognate)

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

← Cornish low (cognate)

← Middle Welsh lleu (inherited)

→ English louse (cognate)

→ Breton laou (cognate)

→ Welsh lleuen (affix)

→ Welsh lleua (affix)

→ Norwegian Nynorsk lus (cognate)