DAGON is a 5 letter word that starts with D.

1. \Da"gon\ (d[=a]"g[o^]n), [Heb. D[=a]gon, fr. dag a fish:
   cf. Gr. Dagw`n.]
   The national god of the Philistines, represented with the
   face and hands and upper part of a man, and the tail of a
   fish. --W. Smith.
   
         This day a solemn feast the people hold To Dagon, their
         sea idol.                                --Milton.
   
         They brought it into the house of Dagon. --1 Sam. v. 2.
   
   

2. \Dag"on\ (d[a^]g"[o^]n), n. [See {Dag} a loose end.]
   A slip or piece. [Obs.] --Chaucer.
   
   

little fish; diminutive from dag = a fish, the fish-god; the national god of the Philistines (Judg. 16:23). This idol had the body of a fish with the head and hands of a man. It was an Assyrio-Babylonian deity, the worship of which was introduced among the Philistines through Chaldea. The most famous of the temples of Dagon were at Gaza (Judg. 16:23-30) and Ashdod (1 Sam. 5:1-7). (See FISH.)