They named it Dan, after their forefather Dan, who was born to Israel--though the city was formerly named Laish.

Genesis 14:14
And when Abram heard that his relative had been captured, he mobilized the 318 trained men born in his household, and they set out in pursuit as far as Dan.

Joshua 19:47
(Later, when the territory of the Danites was lost to them, they went up and fought against Leshem, captured it, and put it to the sword. So they took possession of Leshem, settled there, and renamed it after their father Dan.)

Judges 18:7
So the five men departed and came to Laish, where they saw that the people were living securely, like the Sidonians, tranquil and unsuspecting. There was nothing lacking in the land and no oppressive ruler. And they were far away from the Sidonians and had no alliance with anyone.

1 Kings 15:20
And Ben-hadad listened to King Asa and sent the commanders of his armies against the cities of Israel, conquering Ijon, Dan, Abel-beth-maacah, and the whole land of Naphtali, including the region of Chinnereth.

Jeremiah 8:16
The snorting of enemy horses is heard from Dan. At the sound of the neighing of mighty steeds, the whole land quakes. They come to devour the land and everything in it, the city and all who dwell in it.

And they called the name of the city Dan, after the name of Dan their father, who was born to Israel: however, the name of the city was Laish at the first.