The meaning of IMO is “in my opinion”.
It is essentially a quick disclaimer before you begin to actually be sincere and speak your mind.
The first recorded case of the abbreviation “imo” can be traced back to the 1980’s and it was further popularized in the 90’s, when chatrooms, message boards and forums started to be populated.
In the 2000’s it spread further, through texting.
It appeared on Urban Dictionary at the very beginning of the 2000’s, as early as 2003.
Today, “imo” can be encountered all across the internet, from tweets, to posts on Facebook, threads on Reddit, as well as chats with your friends.
Sometimes, it can even be encountered in a real life conversation as well, since “imo” is a rather popular abbreviation.