É realmente uma função chamada module
. Aparece nas variáveis de ambiente quando você exporta uma função.
$ test() { echo test; }
$ export -f test
$ env | sed -n '/test/{N;p}'
test=() { echo test
}
Em documentação do bash - export :
export
export [-fn] [-p] [name[=value]]
Mark each name to be passed to child processes in the environment. If the -f option is supplied, the names refer to shell functions; otherwise the names refer to shell variables. The -n option means to no longer mark each name for export. If no names are supplied, or if the -p option is given, a list of exported names is displayed. The -p option displays output in a form that may be reused as input. If a variable name is followed by =value, the value of the variable is set to value.
The return status is zero unless an invalid option is supplied, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a shell function.