تعريف ومعنى "[fall] out with {one's} bread and butter"

What is the origin of the idiom "fall out with one's bread and butter" and when to use it?

The idiom "fall out with one's bread and butter" is a metaphorical expression that refers to a situation where someone has a major disagreement or conflict with their primary source of income or livelihood. The exact origin of the idiom is unclear, but it likely dates back to the early 20th century. It is typically used to describe a situation where someone has a falling out or dispute with their employer, main client, or primary source of income. It can be used in both formal and informal contexts.