The Collaborative International Dictionary of English v.0.48:

Bertha \Ber"tha\, n. [F. berthe, fr. Berthe, a woman's name.]
   A kind of collar or cape worn by ladies.
   [1913 Webster]

   Big Bertha, n. a large cannon used by the German army
      during World War I.
      [PJC]
      [1913 Webster]