One etiquette coach on Tic Toc @apuasiwine advises that there is actually a specific way to butter your bread. To stay classy, you should never butter the whole slice at once. Instead, the bread should be broken into pieces and buttered individually.
In these days of economic austerity in the UK, you may be thankful that you have bread to butter and not be too fussed about the manner of preparing it.
You may stay in a job you dislike, because you know which side your bread is buttered. In this context the words may not be taken literally. The expression “to know which side your bread is buttered” is an idiom. An idiom is a phrase, which has a meaning other than the literal use of the words.
This idiom was first used in John Heywoods Proverbs, published in 1546 “I knowe on whiche syde my breade is buttred” , meaning that he knew the course of action that was in his best interests. He lived at a time of religious schism and served as a playwright and musician in both Catholic and Protestant regimes.
Despite knowing which side his bread was buttered, he was once arrested for being part of a plot to have Cranmer, the Archbishop of Canterbury charged with heresy! He was acquitted on this, but as a devout Catholic, he was finally forced to flee to Belgium, due to the Act of Uniformity against Catholics passed in 1564. His grandson was John Donne, the metaphysical poet, who joined the Church of England and became Dean of St. Pauls.
In times when you could be executed for treason or heresy, it was indeed essential to know what side your bread was buttered. never mind about how to slice it!