fierceness (uncountable)

1. The state of being fierce.
   • 1749, [John Cleland], “(Please specify the letter or volume)”, in Memoirs of a Woman of Pleasure [Fanny Hill], London: Printed [by Thomas Parker] for G. Fenton [i.e., Fenton and Ralph Griffiths] […], OCLC 731622352 ↗:

     I stroked it gently, on which the mutinous rogue seemed to swell, and gather a new degree of fierceness and insolence; so that finding it grew not to be trifled with any longer, I prepar'd for rubbers in good earnest.

• French: acharnement