"Perk up" originally meant "to become more alert or lively". It's believed to have originated in the early 19th century, possibly connected to the "perk" in "perky", which itself might be related to the verb "perk" meaning "to lift or raise".
Over time, "perk up" became associated with things that made people more lively or cheerful, such as a cup of coffee or a good meal. This led to the slang use of "perk" to refer to something that provides an added benefit or pleasure, like a bonus at work or a freebie.
Here's a timeline of how "perk" likely evolved:
* Early 19th century: "Perk up" meaning "to become more alert or lively" enters the language.
* Mid-19th century: "Perk" starts to be used as a noun meaning "something that perks someone up", often in the context of food or drink.
* Late 19th century/early 20th century: "Perk" becomes more widely used as a slang term for any kind of benefit or privilege, especially in the workplace.
The OED (Oxford English Dictionary) doesn't have a definitive answer on the origin of "perk" in this sense, but it suggests the connection to "perk up" as a likely explanation.