Welsh cul

← Proto-Brythonic *kʉl (inherited)

← Proto-Celtic *koilos (inherited)

← Old Irish cáel (cognate)

→ Welsh culed (suffix)

→ Welsh culach (suffix)

→ Welsh culaf (suffix)

→ Welsh culdir (compound)

→ Irish caol (cognate)

→ Scottish Gaelic caol (cognate)

→ Cornish cul (cognate)

→ Old Irish cáel (cognate)