I'm Just What!!???

So I'm talking to my boss the other day and I'm telling him what a good memo he wrote or some crap and he says to me..."Stop it, you're just blowing smoke up my ass..." what the hell is that supposed to mean? Let's see if I've got this strait... if you are telling someone that they've done a good job, an that someone thinks you are just telling them that to kiss butt an appropriate saying is, you're just blowind smoke up my ass? Now I'm pretty sure that it wouldn't take too much imagination to derive where the term kiss ass, kiss up or brown noser derived from. Pretty obvious there... but this one definitely has me puzzled. I couldn't imagine the value or reason anyone would have to blow smoke up someone's bottom, and I also can't imagine why I just used the words bottom. Perhaps this all derived from a man telling an obviously unattractive woman that she had a hot ass, when in fact she didn't. So maybe the original comment to follow was... "Stop it, you're just adding heat to my ass" and it evolved from there. That's all I've got.