He bought the hill Samaria of Shemer for two talents of silver, and he built on the hill, and called the name of the city that he built after the name of Shemer, the owner of the hill, Samaria. Bible

”built on the hill.” Omri fortified the hill and built his capital city, Samaria, there. It was so well fortified that when it finally fell to the Assyrians, it took the Assyrian army three years to siege it. Samaria so dominated the region that it became the name of the region itself as well as the name of the city.

Commentary for: 1 Kings 16:24