dillon is a surname of irish origin but with breton-norman roots. it is first recorded in ireland with the arrival of sir henry de leon (c.1176 – 1244), of a cadet branch of viscounty of léon, brittany. he arrived in ireland accompanying prince john (later king john) of england. the name evolved into the irish-language "diolun"/english-language "dillon" (not to be confused with the welsh given name dylan). it is particularly common in the meath and westmeath counties of ireland where the dillons were granted vast areas of land. the name is now widespread throughout ireland. the dillon family later became the barons clonbrock and earls of roscommon. the family in ireland was honoured with six compositions (music & poetry) composed by turlough carolan: tiarna duilleain - lord dillon; róis duilleain - lady rose dillon jig; gearalt duilleain - gerald dillon; fainní duilleain - fanny dillon; comhairleoir duilleain - coun. dillon; lúcás ó duilleain - luke dillon.