It's always been my understanding that the word means exactly what it says, ie overnight you abstain from eating (fast) and in the morning you resume eating or 'break your fast'
What Does The Word Breakfast Mean?
I don't really know what it means really but maybe it means breakfast the whole world can share haha
It means to "break" your fast , fast means fasting a religious or a political statement or observance of eating of no food for a specific period of time. So to eat food after a fast is to "break" it . Hence breakfast