Bede

The Nathinnei, however, dwelt in Ophel, etc. The Nathinnei are considered to be the Gibeonites, who served the house of the Lord with faithful devotion according to the arrangement of Joshua the son of Nun. Ophel, however, was a tower, not far from the temple, of enormous height. Hence, Ophel, that is, of darkness, or named after a cloud, because its head rose up to the clouds. …

Commentary on Ezra and Nehemiah ↗