Definition & Meaning of "mark my [word]"

What is the origin of the idiom "mark my word" and when to use it?

The phrase "mark my word" is an idiom that is used to encourage someone to pay attention to a promise, statement, or prediction. The origin of this phrase is not well-documented, but it has been in use for several centuries and is often used to emphasize the speaker's sincerity or confidence in what they are saying.