Old Irish tiug

← Proto-Celtic *tegus (inherited)

← Welsh tew (cognate)

← English thick (cognate)

← Proto-Indo-European *tegus (inherited)

→ English thick (cognate)

→ Breton tev (cognate)

→ Irish tiubh (inherited)

→ Scottish Gaelic tiugh (inherited)

→ Manx çhiu (inherited)

→ Albanian thuk (cognate)