1 Samuel 27:2 - Joseph Benson’s Commentary on the Old and New Testaments

Unto Achish the son of Maoch “Most writers agree that this Achish, to whom David now fled, was not the Achish by whom he was so inhospitably received, and from whom he so narrowly escaped, when he was before at Gath. His being here called Achish the son of Maoch, sufficiently implies him to have been another person; for those words can, in the nature of the thing, have no use but to distinguish this Achish from another of the same name. And indeed this Achish seems as well distinguished from the other by the rest of his character, as by that of the son of Maoch. But this, by the way, is a fair proof that this book was written at the time that it is said to have been written; insomuch as this distinction was information enough to the people of that age, but could neither be given nor received as such either by any writer or reader of any subsequent age.” Delaney.