The names are not entirely arbitrary, though, and the nuances are actually meaningful, and based on real-world behavior.
E.g., "HUP" means hangup, and indeed, that's what you get when your modem hangs up accidentally! When handled by an application, it often is treated appropriately (e.g., the handler might trigger an autosave before quitting).
"INT" means "interrupt", and usage follows that sense -- it more likely than others to be ignored/repurposed (e.g. to quit back to some application prompt rather than killing the application entirely).
"ABRT" means "abort", and is typically used as a last-ditch means of killing the program when an internal error is detected.
"KILL" is more draconian than any other; there is no recovery possible.
E.g., "HUP" means hangup, and indeed, that's what you get when your modem hangs up accidentally! When handled by an application, it often is treated appropriately (e.g., the handler might trigger an autosave before quitting).
"INT" means "interrupt", and usage follows that sense -- it more likely than others to be ignored/repurposed (e.g. to quit back to some application prompt rather than killing the application entirely).
"ABRT" means "abort", and is typically used as a last-ditch means of killing the program when an internal error is detected.
"KILL" is more draconian than any other; there is no recovery possible.
etc.