[c#] What does the M stand for in C# Decimal literal notation?

From C# specifications:

var f = 0f; // float
var d = 0d; // double
var m = 0m; // decimal (money)
var u = 0u; // unsigned int
var l = 0l; // long
var ul = 0ul; // unsigned long

Note that you can use an uppercase or lowercase notation.