What does the word F mean?

Usage examples for F

  1. About ten minutes ago, Major James F. Slater, of the Literates' Guards, arrived with two hundred of his men, to protect the Literates on duty at the store. – Null-ABC by Henry Beam Piper and John Joseph McGuire
  2. They're in Boat F, with us, and we're sure to find them there." – The Star Lord by Boyd Ellanby
  3. Not for you, F. S. Yes, for me, or for anybody. – The Diamond Pin by Carolyn Wells