Why are overloaded methods having a "_s" suffix

[Jojain]

Hello,
The question is in the title. Why are some of the overloaded methods having a "_s" suffix.
For example :
TDataStd_Name has a Set method and two Set_s methods.
It's sometimes confusing because if we use the Set method the code will fail due to type error. (i.e the arguments aren't passed as the right overloaded method)

More important, is this random ? And can it change depending on the OCP version?

[Jojain]

I had the good idea to check others issue after posting mine...
The answer is given here : #15
Methods with "_s" suffix are static methods.