If I remember correctly it's an American term that originated in truck stop cafes where meals were ordered by number. To 86 a meal is to throw it in the trash. It follows that 86 is worthless, no better than rubbish. Example: If you were to 86 this answer it would probably be appropriate.
Also out of the aa big book page 86 telling u to throw or discard stuff away
I'm not entirely sure it is always used as a "derogatory" statement.
In some respects there are ideas, inventions, and things that just need to be "86'd" because they are obsolete or didn't fix the problem.
Here are some great possible references to that term:
Especially look into the possible etymologies.