I am calling a BIG bullshit flag on a lot of reply's here WITHOUT EVEN READING THEM.
The term "sass" is complete, and utter bullshit and should be avoided at all costs. Where it originated from and what it currently means have zero correlation. It is like using the "stack" terms (e.g., single stack, double stack, triple stack, and so on and so forth); the terms are used by dealers to increase some form of "marketing" hype to sell a product to an uneducated buyer.
Now...
Some people will say "sass" is sassafras oil (Saffrole) which is so fucking retarded it hurts and angers me every single time I have read it. Saffrole is the precursor to MDMA, it is not psychoactive, and is a known carcinogen.
I have heard people say "sass" is MDMA that was not cleaned at the final step of the synth (more than likely they are trying to say that it was not washed in acetone or recrystallized).
Others will swear that "sass" is MDA (3,4-methylenedioxyamphetamine -if I am correct) which I am pretty sure is a precursor to MDMA (I am also pretty sure it is a homologue of MDMA).
The kicker.. *drum roll* Are you ready ladies and gentlemen? The greatest thing on earth... So I have come to understand, depending on your location, "sass" is simply a regional term for MDMA (as some people say molly, some say sass). If you go to festivals, you will more than likely hear the term sass! Also, some southern areas of the USA refer to MDMA as sass, generally in the northern regions of the USA it is referred to as molly (this is not always correct, but merely a rule of thumb).
It is simply different terminology (e, adam, xtc, molly, sass, moon rocks, shards, rolls, beans, blah blah blah).
The original term "Sass" was indeed MDA, this is no longer the case.
EDIT:
It is like buying ecstasy (pills). Someone could be selling you a "triple stack", and it could be baking soda and caffeine. People will sell shit with a name merely to sell shit with no regards to what it contains in reality.