Does anyone really call him 'of Rotterdam'? It took me a minute to be sure that it was the same person. After all, he had a perfectly good first name - 'Desiderius'.
see:
Erasmus of Rotterdam, the Man and the Scholar : Proceedings of the Symposium Held at the Erasmus University, Rotterdam, 9-11 November 1986
by J. Sperna Weiland (Editor), W. Th. M. Frijhoff (Editor), J. spern Weiland