McGillis is either Irish or Scottish. Gillis might be a shortened form of that. Kelly McGillis of “The Witness” with Harrison Ford and “Top Gun”.
Haskel could be English, Hebrew/Israeli/Jewish, or a shortened form of an English/Scottish name.
Eddie Haskel became a police officer. Good for him.
Haskell is also a first name.
Names are sometimes misleading as to what their origins are as my family’s name was modified by Immigration when my grandfather came here in the late 1890’s or early 1900’s wherein his father’s name was spelled in the original Anglicized form (and he came earlier in order to bring the kids over once he had a job, which he did).
The Haskell that sticks in my mind is Sen.Floyd Haskell (D-Colo.) who bucked the 1972 Nixon landslide by narrowly edging out conservative Republican incumbent Gordon Allot and then pushes a far-left agenda until Bill Armstrong ousted him in 1978.
“Gillis might be a shortened form of that” or it could be a shortened form of the Yiddish “gillisse” (balded) as indeed the actor playing Dobie was, so as to hide with a razor-close crew cut his dark hair, in a part calling for a blonde. It’s less of a leap than from Julius to “Groucho” Marx.