The land now known as Boseong was called Bokhol-gun under the kingdom of Baekje. The character "hol" meant fortress, and it is presumed that the region's association with a fortress carried over into its later name, but exactly why the two characters forming "Boseong" were chosen remains unclear in the historical record. This region received its present name in 757 (the 16th year of King Gyeongdeok's reign of Silla). King Gyeongdeok undertook a sweeping project to standardize place names across the country into Sino-Korean form, and in the course of this project, Bokhol-gun was renamed Boseong-gun.
The name thus acquired did not remain entirely fixed thereafter. In 996 (the 15th year of King Seongjong's reign of Goryeo), it was briefly renamed Paeju, with a governor dispatched to oversee it. But through these various shifts, the name "Boseong" itself ultimately survived and continues in use today. A name whose precise origin remains uncertain has endured for nearly 1,300 years regardless — and in that endurance alone, it testifies to the sheer span of time this land has passed through.