Christian Jarrett,Research Digest
When I was at primary school, we used to type out the word BOOBIES using upside-down digits on our electronic calculators and we thought it was hilarious. This was an all-boys school in the late 80s, or sever us some slack. And besides,maybe we weren't so daft. The word (although spelt differently as Booby) was among the top-three most funny words as identified in a unusual paper in Behaviour Research, which is the first in-depth investigation of the perceived funniness of individual English words.
Source: realclearscience.com