"The Non-Pretentious and Non-Dumb Thread" might work ...
At the risk of derailing this thread even further, I thought that there was doubt/confusion as to whether Onan was "self-pleasuring" (there's yet another expression for you!) or whether he was practicing premature withdrawal, when he spilled his seed upon the ground?
The main issue, according to the Bible, was that by doing what he did, Onan was wasting his seed instead of trying to have more children, which is what God/Yahweh wanted him to do. The Catholic aversion to birth control stems from that incident, I believe.