Naming Conventions
I have a vague recollection from somewhere that the units that are named after a person use a Capital first letter, and thus a Capital abbreviation
Thus:
V for Volts (named after Alessandro Volta),
J for Joule (James Prescott Joule),
W for Watt (James Watt),
etc.
But lower case for other units.
Thus:
m for metre,
g for gram,
etc.