Dillon in Irish

Woulfe (1923) mentions it as been a French name in origin but containing a Germanic element (from Frankish? or perhaps Norse given Norman connection)

---
DÍOLMHAIN, DÍOLÚN—VIII—Dylun, Dilloun, Dillon; 'son of Dillon' (a Norman-French personal name formed from an old Teutonic personal name Dill, Dillo, Dilli, by the addition of the French diminutive termination '-on.' Dille appears as a surname in older English records, now written Dill; and Dilkok, another diminutive of the same name, now represented by the surname Dilcock in England, is found in the Patent and Close Rolls of Ireland, Henry II—Henry VII. Díolmhain, the older Irish spelling of the name, may be due to an attempt to assimilate it to the Irish word díolmhain). The Dillons came to Ireland at the time of the Anglo-Norman invasion. Sir Henry Dillon received from King John large grants of land in Westmeath and Annaly, known in later times as Dillon's Country, and his descendants were barons of Kilkenny West. A branch of the family also settled in Co. Mayo. In the 17th and 18th centuries, the Dillons were distinguished in the service of continental powers.
--

Obviously the above is for the surname.