Origin: Irish, Welsh
Meaning: debated, and numerous.
Have you ever come across a name you think you know about but than you look it up and you realize that there are a lot of contradictory information about it? Well, this name was one of them. Originally I thought it was a variant spelling of Welsh Dylan (and it kind of is) but it also seems to have a completely different origin and meaning(s). So it’s of Irish origin, either coming from dealan “a flash of lightning” or an Irish word meaning “faithful, loyal” (http://www.babynamesofireland.com/dillon)
According to surnamedb.com, ancestry.com, and houseofnames.com, Dillon either comes from Dilwyn (or Dilun), a locational name referring to someone who lived near the town, which comes from Old English diglum meaning “recess” or”retreat”- referring to someone who lives at the shady or secret places (http://www.ancestry.com/name-origin?surname=dillon).
It could also come from a Germanic personal name, Dillo, meaning “destroyer”.
It could also be a transposition of de Leon, a place name referring to someone who came from a town in Lyon, France, or a nickname referring to a fierce/brave warrior, from the animal lion, introduced during the Anglo-Norman invasion of 1169.
Dillon is also an Anglicization of Gaelic O’Duilleain meaning “descendant of the blind one”.
Of course, like I said, it could be a variant spelling of Welsh Dylan, meaning “great tide/flow/sea” or “influence”. More on that in a separate post, though.