[meteorite-list] Definition of "Hammer"

[Anita D. Westlake]

I read somewhere that a "Hammer" in the meteorite world came from a
meteorite striking:

H = Human
A = Animal
M = Man-
M = Made
E = ?
R = ?

Or did I just make that up? If it's true, does anyone know what the "E" and
"R" stand for?

Anita