Nibbles, 6.5 5.5 bytes (11 nibbles)

Edit: -2 bytes by using transpose, inspired by Jonathan Allan's Jelly answer

|$>2`'=~$$

|$              # filter each word int the input by
      =~$       #   group the letters by
         $      #     themselves,
    `'          #   transpose this list of lists,
  >2            #   and remove the first 2 elements
                #   (so if there is at least one letter
                #   present >2 times, the resulting 
                #   list will have nonzero length)