What is upon? How to use in English

The origin of the word "upon" is fascinating! It's an English preposition that has been in use for over 1,000 years. The modern word "upon" comes from the Old English phrase "up on," which meant "upwardly" or "above." This phrase was used to indicate movement upward or direction above something. Over time, the phrase "up on" underwent a process called grammaticalization, where a phrase becomes a single word with a specific grammatical function. In the 11th century, "up on" started to be written as a single word, "upon," and its meaning expanded to include ideas of time, space, and direction. Today, "upon" is used to indicate various relationships, such as location, time, or circumstances, as in "I'll be upon the mountain" or "I'm thinking upon the future." Despite its evolution, the foundation of "upon" remains rooted in its Old English origins.