The text says that Samson went down to Timnah.
His descent is topographical, since Timnah, nine-and-a-half kilometres west of Samson’s hometown of Zorah, is at a lower altitude than Zorah; when he switches direction and returns to Israel he is said to go up.
Yet Timnah, though in Israelite territory (suggested by Joshua 15:10), was still in the hands of the Philistines,1 and so the verb to go down
is used also symbolically to point to Samson’s behaviour in the narrative: he was going down spiritually. There is a lot of going down
in this narrative; the verb is repeated five times (Judges 14:1, Judges 14:5, Judges 14:7, Judges 14:19; Judges 15:8). Samson is on a spiritual descent toward moral chaos, and not just for himself but for Israel as a whole.2
1 Samson went down to Timnah, and at Timnah he saw one of the daughters of the Philistines.