When people use ham radios, they usually sign off by saying 73.
Its origins lie in the days of the telegraph, wherein operators noticed they had to send some common messages repeatedly. So to save bandwidth and effort, they came up with shorthand.
You can read about it here: https://hamradioprep.com/what-does-73-mean/
I am currently implementing compression into the Meshtastic firmware. You might be wondering what’s the point of shorthand then?
Just imagine you are in an emergency and/or you have a weak signal. Sending a message with 15 bytes might fail, but sending a message with 2 bytes might succeed. We can easily program shorthand into the Meshtastic iOS/Android apps (to save space on the firmware on Meshtastic boards). For example, you could select the shorthand message (“Man down, medical evac needed urgently”) in the app, and the mesh would transmit 2 bytes, for example (“11”) corresponding to this message. I think this is useful and necessary and vital for situations where the signal is weak/unstable. No matter what compression method I use, I cannot compress messages like these from 20 bytes to 2 bytes. So it’s better to have a long list of shorthands loaded into each app.