"Kedagh,Céadach m[ale] a well-used name in the later Middle Ages. Its meaning is unclear, but it may come from a word for 'first', or a word meaning 'hundred'". Julia Cresswell, "Irish First Names". Edward MacLysaght, discussing the surname Keady ("Surnames of Ireland") writes "Céadach was a personal name (from céad, hundred) popular with the O'Mores of Leix with whom the MacKeadys were associated." Interesting to see an early (pre-surnames)instance of the name.