Named after Klosterstraße, the street of the Graues Kloster.
'Kloster' means monastery: the street takes its name from the Graues Kloster ('Grey Monastery') of the Franciscans, known as Grey Monks for the colour of their habits, who received the site here in 1271. Only the ruin of its church survives. Before the name Klosterstraße came into use in the early 18th century, its sections were called things like 'Neben dem Grauen Kloster' (beside the Grey Monastery).