Can I define two exact same commands using /newcommand with the only difference is one is lower case and the other is upper case

In my macro file, I have defined two commands

\newcommand{\SO}[1]{\mathsf{SO}(#1)}\newcommand{\so}[1]{\mathfrak{so}(#1)}

There are two exact same commands with the only difference is in case. When I use it in my main file, I get the following error:

LaTeX Error: Command \so already defined

The worrying part is, this was working before but now it has stopped working. Am I missing some package or something? If I do, what package would it be?

Thanks!