Albert Barnes Commentary Judges 16:23

"And the lords of the Philistines gathered them together to offer a great sacrifice unto Dagon their god, and to rejoice; for they said, Our god hath delivered Samson our enemy into our hand." — Judges 16:23 (ASV)

Dagon was the national idol of the Philistines (1 Chronicles 10:10), so named from Dag, a fish. The description of Dagon in his temple at Ashdod (1 Samuel 5:4) perfectly matches the depictions of a fish-god on the walls of Khorsabad, on slabs at Kouyunjik, and on various antique cylinders and gems. In these representations, the figures vary. Some have a human form down to the waist, with that of a fish below the waist; others have a human head, arms, and legs, appearing to grow out of a fish’s body, and so arranged that the fish’s head forms a kind of miter on the man’s head, while the body and fins form a kind of cloak hanging down behind.