John Gill Commentary Joshua 15:15

"And he went up thence against the inhabitants of Debir: now the name of Debir beforetime was Kiriath-sepher." — Joshua 15:15 (ASV)

And he went up from there to the inhabitants of Debir
Having conquered Hebron, and got possession of that, Caleb marched to Debir, a city not many miles from Hebron, and seems to have been in the country, and part of the land, which was given him; of which (See Gill on Joshua 10:38);

and the name of Debir before [was] Kirjathsepher ;
or "the city of books"; either a place of literature, a sort of an academy, or where was a public library; the Targum calls it Kirjatharche, or the city of the archives, in which were laid up the public records of the Canaanites; the same is called Kirjathsannah for the like reason, (See Gill on Joshua 15:49).