1. The Afrikaans word for banana is "piesang".
2. Rama is a popular brand of margarine in South Africa
3. Margarine is so common as a butter replacement here that many people refer to it *as* "butter" even though it actually isn't.
4. Therefore, "piesangbotter" = "Banana butter".
5. But "piesang" is also a euphemism for "penis", so "piesangbotter / piesang butter" is... I think you get it. :-)