Surnames tend to come from patronyms/matronyms (named for parentage), toponyms (named for where they are from, live, or work), occupational names, ornamental names (invented largely by the middle class to resemble the names of noble lineages), and of course cognominal surnames, which are generally based on descriptors of the first of their line.

By process of elimination, he's descended from a voyeur.

(Actually it probably came from "Ocga Hill" in Old English, which seemingly was used by anglo colonizers in Ireland)