KAYSER 1. German and Dutch: variant spelling of Dutch Keizer and German Kaiser. 2. Jewish (Ashkenazic): variant of Kaiser.
KAISER 1. German: from Middle High German keiser ‘emperor’, from the Latin imperial title Caesar. This was the title borne by Holy Roman Emperors from Otto I (962) to Francis II (who relinquished the title in 1806). Later, it was borne by the monarch of Bismarck’s united Germany (1871–1918). It is very common as a German surname, originating partly as an occupational name for a servant in the Emperor’s household, partly as a nickname for someone who behaved in an imperious manner, and partly from a house sign. 2. Jewish (Ashkenazic): ornamental name from German Kaiser ‘emperor’, adopted (like Graf, Herzog, etc.) because of its aristocratic connotations. 3. Muslim: from Arabic qay?sar ‘emperor’, which, like 1, is of Latin origin, from the imperial title in the Roman Empire.
Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4