FETTERMAN Americanized form of German Vettermann: variant of Vetter , with the addition of Middle High German man ‘man’. Americanized form of German Fettermann: variant of Fetter 1, with the addition of Middle High German man ‘man’. It is a cognate of 1 above. Jewish (Ashkenazic): nickname for a fat man, a variant of Fetter 2.
O Rly? What a coincidence.