http://en.wikipedia.org/wiki/Thomas_%C3%A0_Kempis

Thomas à Kempis (c. 1380 - 25 July 1471) was a late Medieval Catholic monk and the probable author of The Imitation of Christ, which is one of the best known Christian books on devotion. His name means, "Thomas of Kempen", his home town and in German he is known as Thomas von Kempen. He also is known by various spellings of his family name: Thomas Haemerkken; Thomas Hammerlein; Thomas Hemerken, and Thomas Hämerken.