Pronunciation: [stˈʌmblɪŋ ˌʌp ˈɒn] (IPA) 
The correct spelling of the phrase we commonly hear as "stumbling up on" is "stumbling upon". The "up" in this phrase is an unfortunate mistake that has become quite common. The word "upon" is pronounced /əˈpɒn/, with the stress on the second syllable. The "p" is silent, making it a little tricky to spell. Remember, when you come across this phrase, it's "stumbling upon", not "stumbling up on"!
The term "stumbling upon" is a phrase that refers to an unexpected or accidental encounter with something or someone, typically by chance rather than intent. It is an idiomatic expression that implies finding or coming across something or someone unexpectedly or without intending to do so.
When someone says they "stumbled upon" something, it means they encountered it unexpectedly, as if they had stumbled upon it while walking or navigating through a situation. This phrase is often used to describe a chance discovery or an accidental encounter with something novel, interesting, or valuable. It conveys a sense of surprise or astonishment on the part of the individual.
The act of stumbling upon something does not involve actively searching or seeking it out. It may occur when one is exploring unfamiliar territory, wandering aimlessly, or perhaps undergoing a serendipitous chain of events that leads to an unexpected encounter. The exact circumstances can vary widely, but the common denominator is the element of chance or happenstance.
The metaphorical nature of this expression also suggests that the person may not have anticipated or planned for the consequence or outcome of their encounter. Whether stumbling upon a solution to a problem, an interesting article, or a long-lost friend, the phrase implies an element of unpredictability and unplanned discovery, adding a sense of adventure to the experience.
