The question concerns the definitions of the words in a poem. Here fray means to become unraveled because of constant rubbing. Of course, it is about the rope.
Tarnish means dullness or loss of color. The correct match is to become dull or spoiled after.
In informal meaning, bilge means rubbish and nonsense. However, the bilge itself is a ship's hull where the bottom of the ship meets the vertical sides and dirty water collects to that place.
