The message (stress on the first "e") is a fashionable English word, which in Russian means "message, message". And you did understand correctly: the messenger is a program for the exchange of messages.
What message do I want to convey to you with this article? Very simple: use the Russian word "message" in communicating with people older than 60 years. Well, in the youth get-together, if you want to convey your love message to your message, safely cut your messenger and draw emoji with hearts in front of her.
The message is in the list: Slang