METTLE - sounds like 'MEET' + 'HELL' To MEET HELL one should have the COURAGE TO CARRY ON
Sounds like metal and metals are obviously strong. So, can be related to a strong courageous person.
Reminds of Steel King industrialist Lakshmi Mittal: Symbolic of courage to carry on
meet(guys lets meet up,we all will be a force then)+all(Unity is strength and seems courageous)
in the military they give you a metal for brave deeds
METTLE= MEnTaL courage and spirit....
MET(meat)+LE(in hindi le means take)....people who sell meat say MEAT LE....but they require COURAGE to carry on the business because everytime they have to kill innocent animals
it takes mettle to walk through a field of nettle