La función register_taxonomy y los "labels"

plugin-cpt.php

<?php
/*
Plugin Name:  Plugin CPT y Custom Taxonomies
Plugin URI:   https://silicodevalley.com
Description:  Plugin para aprender a crear CPT y CT con código
Version:      1.0.0
Author:       David Perálvarez
Author URI:   https://silicodevalley.com
License:      GPL2
License URI:  https://www.gnu.org/licenses/gpl-2.0.html
*/

/*
Plugin CPT y Custom Taxonomies is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
any later version.

Plugin CPT y Custom Taxonomies is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Plugin CPT y Custom Taxonomies. If not, see https://www.gnu.org/licenses/gpl-2.0.html.
*/

// Comic Reviews
function comic_review_setup_post_type(){

  $labels = array(
    'name' => __( 'Reseñas', 'scv' ),
    'singular_name' => __( 'Reseña', 'scv' ),
    'add_new' => __( 'Añadir reseña', 'scv' ),
    'add_new_item' => __( 'Añadir nueva reseña', 'scv' ),
    'edit_item' => __( 'Editar reseña', 'scv' ),
    'new_item' => __( 'Nueva reseña', 'scv' ),
    'view_item' => __( 'Ver reseña', 'scv' ),
    'view_items' => __( 'Ver reseñas', 'scv' ),
    'search_items' => __( 'Buscar reseñas', 'scv' ),
    'not_found' => __( 'No se encontraron reseñas', 'scv' ),
    'not_found_in_trash' => __( 'Ninguna reseña encontrada en la papelera', 'scv' ),
    'all_items' => __( 'Todas las reseñas', 'scv' ),
    'insert_into_item' => __( 'Insertar en la reseña', 'scv' ),
    'filter_items_list' => __( 'Lista de reseñas filtrada', 'scv' ),
    'items_list_navigation' => __( 'Navegación por el listado de reseñas', 'scv' ),
    'items_list' => __( 'Lista de reseñas', 'scv' ),
  );

  $args = array(
    'public' => true,
    'labels' => $labels,
    'menu_position' => 5,
    'menu_icon' => 'dashicons-star-half',
    'hierarchical' => false,
    'supports' => array(
      'title','editor','author','thumbnail','excerpt','custom-fields','comments','revisions',
    ),
    'has_archive' => true,
    'rewrite' => array(
      'slug' => __( 'reviews', 'scv' ),
    ),
  );

  // poner prefijo, max 20
  register_post_type( 'scv_comic_review', $args );


  // Author Taxonomy
  $labelsAuthor = array(
    'name' => __( 'Autores', 'scv' ),
    'singular_name' => __( 'Autor', 'scv' ),
    //'menu_name' => __( 'Autores', 'scv' ), //default: 'name'
    'all_items' => __( 'Todos los autores', 'scv' ),
    'edit_item' => __( 'Editar autor', 'scv' ),
    'view_item' => __( 'Ver autor', 'scv' ),
    'update_item' => __( 'Actualizar autor', 'scv' ),
    'add_new_item' => __( 'Añadir nuevo autor', 'scv' ),
    'new_item_name' => __( 'Nombre del nuevo autor', 'scv' ),
    //'parent_item' => __( 'Autor Padre', 'scv' ), //jerárquica
    //'parent_item_colon' => __( 'Autor Padre:', 'scv' ), //jerárquica
    'search_items' => __( 'Buscar autores', 'scv' ),
    'popular_items' => __( 'Autores populares', 'scv' ), //no jerárquica
    'add_or_remove_items' => __( 'Añadir o eliminar autores', 'scv' ), //no jerárquica / no javascript
    'choose_from_most_used' => __( 'Elegir entre los autores más utilizados', 'scv' ),
    'not_found' => __( 'No se han encontrado autores.', 'scv' ),
  );

  $argsAuthor = array(
    'public' => true,
    'labels' => $labelsAuthor,
  );
  // poner prefijo, max 32
  register_taxonomy( 'scv_comic_author', array('scv_comic_review'), $argsAuthor );
  register_taxonomy_for_object_type( 'scv_comic_author', 'scv_comic_review');

  // Genre Taxonomy
  $labelsGenre = array(
    'name' => __( 'Géneros', 'scv' ),
    'singular_name' => __( 'Género', 'scv' ),
    'all_items' => __( 'Todos los géneros', 'scv' ),
    'edit_item' => __( 'Editar género', 'scv' ),
    'view_item' => __( 'Ver género', 'scv' ),
    'update_item' => __( 'Actualizar género', 'scv' ),
    'add_new_item' => __( 'Añadir nuevo género', 'scv' ),
    'new_item_name' => __( 'Nombre del nuevo género', 'scv' ),
    'parent_item' => __( 'Género Padre', 'scv' ), //jerárquica
    'parent_item_colon' => __( 'Género Padre:', 'scv' ), //jerárquica
    'search_items' => __( 'Buscar géneros', 'scv' ),
    'choose_from_most_used' => __( 'Elegir entre los géneros más utilizados', 'scv' ),
    'not_found' => __( 'No se han encontrado géneros.', 'scv' ),
  );

  $argsGenre = array(
    'public' => true,
    'labels' => $labelsGenre,
  );
  // poner prefijo, max 32
  register_taxonomy( 'scv_comic_genre', array('scv_comic_review'), $argsGenre );
  register_taxonomy_for_object_type( 'scv_comic_genre', 'scv_comic_review');
}

add_action( 'init', 'comic_review_setup_post_type' );

// Flushing Rewrite on Activation/Deactivation (plugin)
register_deactivation_hook( __FILE__, 'flush_rewrite_rules' );
register_activation_hook( __FILE__, 'scv_rewrite_flush' );

// Flushing Rewrite on switch theme
//add_action( 'after_switch_theme', 'scv_rewrite_flush' );

function scv_rewrite_flush(){
  comic_review_setup_post_type();
  // limpia las reglas de reescritura (enlace permanentes)
  // actualiza el fichero .htaccess
  flush_rewrite_rules();
}