First you need to know about the fish with the scientific name of _Boops boops_, which is real. This means ‘cow face cow face’ and is not a joke. If you like you can pronounce it ‘bow-ops’ to emphasise the etymology, as in ‘coöperation’. The ‘ops’ part is the bit that means ‘face’ in Ancient Greek.

The joke is this: that the etymology of _oops_ is ‘egg face’ — from the phrase “there is egg on my face” — and is pronounced oöps. (The Ancient Greek word for egg is ‘oon’ which gives us ‘oomancy’, ‘divination by eggs’.)