Note: Since 23w06a, these death messages are no longer technically unused, since you can obtain them by using the new /damage command. I am not sure whether this ticket should still be considered valid though.

A lot of entity damage sources have not always been entity damage sources, since they were once environmental damage sources. This caused their ".player" death message variants to become unused, but their translation strings still exist.

Affected death messages:

• death.attack.sting.player (well, this one was always unused, so it doesn't have the same history as the rest)
• death.attack.fireworks.player
• death.attack.sonic_boom.player
• death.attack.anvil.player
• death.attack.fallingBlock.player
• death.attack.fallingStalactite.player