1. Create custom action in function.php, which checks current page type (if it's category or tag page).
   

    function hidden_term_name_action() {
   
        if( is_category() || is_tag() ){
   
            $term_id = get_queried_object_id();
            $term = get_term($term_id);
            if($term){
                echo sprintf('<h1 style="display:none;">%s</h1>', esc_attr($term->name));
            }
   
    }
   
    add_action('hidden_term_name', 'hidden_term_name_action');
   

2. Paste this code in header.php, which fires this action and pastes term title inside hidden h1 tag.
   

    <?php do_action('hidden_term_name'); ?>
   

P.S. Not tested, but give it a try.

1. Create custom action in function.php, which checks current page type (if it's category or tag page).
   

    function hidden_term_name_action() {
   
        if( is_category() || is_tag() ){
   
            $term_id = get_queried_object_id();
            $term = get_term($term_id);
            if($term){
                echo sprintf('<h1 style="display:none;">%s</h1>', esc_attr($term->name));
            }
        }
   
    }
   
    add_action('hidden_term_name', 'hidden_term_name_action');
   

2. Paste this code in header.php, which fires this action and pastes term title inside hidden h1 tag.
   

    <?php do_action('hidden_term_name'); ?>
   

P.S. Not tested, but give it a try.