Origin of the name Morris:

Variant of Maurice, a borrowing from the French which is derived from the Late Latin Mauritius (Moorish), a derivative of Maurus (a Moor). The Moors were a Muslim people of mixed Arab and Berber descent; thus the name came to mean "dark" or "swarthy" in reference to their coloring. Maurice was introduced to Britain by the Normans and underwent several variant spellings before returning to the original form.

From A World of Baby Names by Teresa Norman.