Well okay, but there are definitely other words that rhyme with yank that could have yielded more flattering results. Hell, just using tank, then tying that to a Sherman tank and calling Americans Shermies could have worked. But someone chose septic, and it's hard to imagine that wasn't intentional.       
          
The most overt example I remember was fictional from Oceans 11 when the black explosion man says that if a certain thing happens they'd be in Barney, as in Barney Rubble with Rubble rhyming with trouble. So Barney meant trouble. That was pretty cool.