According to the biblical story, Samson was given extraordinary physical strength through God. First he fell in love with a woman named Timnah, a Philistine, and weds her-- at the wedding reception, he promises a group of Philistines that he will provide them with thirty sets of clothes if they can solve a riddle. They are unable to solve it, but they implore Timnah to get the answer from him-- she does, and tells them, and Samson becomes furious because he doesn't have clothing to give to them.
He leaves town and kills thirty other men in a nearby village, steals their clothing, but when he returns, Timnah is now married to a friend of his. Enraged, he ultimately ends up killing a thousand of the Philistines.
When he goes to Gaza, Samson meets and falls in love with Delilah. The Philistines convince her to get him to tell her the source of his power-- he tells her it's his hair (however, it was not *really* in his hair, but because he had already broken two laws of the Nazarite. This was enough for God to take his power away from him).
Delilah cuts off all of Samson's hair, and then he is captured by the Philistines, who gouge out his eyeballs. However, the way he dies is by pulling down the two central pillars in a temple.
This seems to be referred to in the song with the lines "Oh, we couldn't bring the columns down / Yeah, we couldn't destroy a single one."
I think the narrator of this song-- Delilah-- is lamenting about what could have been. Because she secretly did love Samson. All of the stories say that Samson loved Delilah, and make no mention of her returning the feelings. The lyric "I loved you first" seems to imply that not only did she love him back, but she loved him before he even loved her.
As I see it, this song is about how she imagined a different ending for their tragic romance. In this version, after she cuts his...