Dynamically define command name from a parameter, creating a command that can't be called more than once

Question

I'm creating a lot of commands dynamically in a very big LaTeX project, and i want to ensure these commands are only called once in the entire project. I can already create single-use commands thanks to this code (which i included in the MWE) : https://tex.stackexchange.com/a/410816/235171.

How would one exploit it to create single-use commands which names are created via a parameter within another command ? I also want my commands to be with a leading backslash.

MWE :

\documentclass{article}
% Preprocessor code
\usepackage{xparse}
\ExplSyntaxOn
\cs_set_protected:Nn \my_optional_processor:n
  {
    \str_if_eq:nnTF { #1 } { \use:c { c_novalue_tl } }
      { \def \ProcessedArgument {} }
      { \def \ProcessedArgument { [#1] } }
  }
\ExplSyntaxOff
\newcommand\MyStarredProcessor[1]{%
  \IfBooleanTF{#1}
    {\def\ProcessedArgument{}}
    {\def\ProcessedArgument{}}}
\ExplSyntaxOn
\NewDocumentCommand{\newonetimecommand}
  { t!
    >{\MyStarredProcessor}s
    m
    >{\my_optional_processor:n}O{ \use:c { c_novalue_tl } }
    >{\my_optional_processor:n}+O{ \use:c { c_novalue_tl } }
    +m }{%
  \newcommand#2#3#4#5{%
    #6%
    \IfBooleanTF{#1}{\gdef}{\def}#3{%
      \GenericError{}
        {Error:~\string#3~used~twice!}
        {Command~was~setup~to~be~usable~only~once}{}%
    }%
  }}
\ExplSyntaxOff
% Failed attempt
\newcommand{\createCommand}[1]{%
    \expandafter\newonetimecommand!*\csname\string#1\endcsname{
        I am writing #1 !
    }
}
\begin{document}
    \createCommand{foo} % Creates \foo
    \foo % Can be called once
    \foo % Should produce an error thanks to the use of \newonetimecommand!*
\end{document}

Produced error :

Command \csname already defined. Or name \end... illegal