Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
ANNAN
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
(origin: Local) A river and borough of Scotland. From the Gaelic aon, aon, one, one, or the river that divides the dale in two shares. Amhan, Avon, or An-oun, in Gaelic, may signify the slow running water; a gentle river.
Origin: English
Region of origin: British Isles
Country of origin: England
Religion of origin: Christian
Language of origin: English