N. stands (as it constantly did in MS.) for "nomen" or name; M. for N.
N., "nomina" or names. You will observe that in black letter the forms
of N and M are so very similar that by an easy contraction double N
would pass into M, and thus the contracted form N. N. for "nomina" might
have come into M. Corroborating this is the fact that the answer to What
is your name? stands thus: Answer N. or M., and not M. or N.