The "V" stands for Vengeance
It is not a military custom it's a military command, 'stand at ease' means to relax from the 'stand to attention' command.
Depending on how it's used, it could stand for "Military Specification", meaning the ability to withstand shock, dust, or harsh environments.
Military Specification
MPO stand for Military Police Officers.
Doctor
This Is Where I Stand was created in 2001.
Stand By was created in 2011.
I Stand With You was created in 1988.
Where We Stand was created in 1999.
Stand Strong Stand Proud was created in 1982.
It is the military term for a 'search and rescue dot.'
Stand on It was created in 1986-04.