What is come upon? How to use in English

The phrase "come upon" is a phrasal verb in the English language that is used to describe the unexpected discovery or encounter of something. It is formed from the words "come" and "upon," which originally had separate meanings. In Old English, "ciman" (an earlier form of "come") meant "to move towards," while "on" (an ancestor of "upon") meant "on." These words were combined to create phrases like "ciman on" or "cymon on," which meant "approaching or arriving at" and were used to indicate movement towards something. Over time, the phrases "ciman on" and "cymon on" began to lose their separate meanings and merged into a single expression, "come upon." This process is known as grammaticalization, where a group of words or grammatical elements come together to form a new, complex unit with a unique meaning. Nowadays, "come upon" is widely used in English as a prepositional phrasal verb to indicate the accidental discovery or chance encounter of something. The use of "come" emphasizes the unexpected nature of the discovery, while "upon" shows that the discoverer has arrived at the object or location where it is found.