The words "poser" and "poseur" are often confused with each other, but they have slightly different origins and meanings.
"Poser" comes from the English verb "to pose," meaning to pretend or act falsely. A poser is someone who pretends to be something they're not, often to impress others.
"Poseur," on the other hand, comes from the French word "poseur," meaning "one who poses" or "a pretender." In English, a poseur is also someone who pretends to be something they're not, but the connotation is more nuanced, implying a more affected or exaggerated pretension.
The reason "poseur" is spelled with a "u" is due to its French origin. In French, the verb "poser" (to pose) is related to the noun "poseur" (one who poses), and the spelling was retained when the word was borrowed into English.
So, while both words refer to someone who pretends to be something they're not, "poser" is more straightforward, while "poseur" carries a slightly more sophisticated, pretentious connotation.