Source : Webster's Revised Unabridged Dictionary (1913)

Odd Fellow \Odd" Fel`low\
   A member of a secret order, or fraternity, styled the
   Independent Order of Odd Fellows, established for mutual aid
   and social enjoyment.

Source : WordNet®

odd fellow
     n : someone regarded as eccentric or crazy and standing out from
         a group [syn: {kook}, {odd fish}, {queer bird}, {queer
         duck}, {odd man out}]