setCsrfTokenName(string $tokenName)

Specify the token name for CSRF protection. This field will be sent in every AJAX request if the token value is not empty. The token value can be set with setCsrfTokenValue. The default CSRF token name is __csrf.

As it doesn't make too much sense to use setCsrfTokenName without setCsrfTokenValue there are examples of usage at the page of: setCsrfTokenValue