Delilah’s incessant nagging recalls the tactic used by Samson's former wife, the Timnite (Judges 14:17). Indeed, the same verb is used on both occasions. And as with his wife, so here, the tactic works. Delilah wears him down, to the point where he breaks.
16 And when she pressed him hard with her words day after day, and urged him, his soul was vexed to death.