 Old Sarum, Wiltshire, Latin "Sorviodūnum"
Second element from Celtic *"dūnon" 'fortress'
First element conjectured to be Celtic for 'victorious', 'strength' or 'dry' (theories).Second element is Celtic *"dūnon" 'fortress'.From Celtic *"seno-" 'old' + *"dūnon" 'fortress'
Possibly from Celtic *"tames-" 'dark' ("cf".