Stories We Like: A Guide to the Comma
"In the exact sense, a tyrant is an individual who arrogates to himself the royal authority without having a right to it. This is how the Greeks understood the word 'tyrant': they applied it indifferently to good and bad princes whose authority was not legitimate." [Rousseau, "The Social Contract"]The spelling with -t arose in O.Fr. by analogy with prp. endings in -ant. Fem. form tyranness is recorded from 1590 (Spenser); cf. M.L. tyrannissa (1372).