How can I see my theme’s text domain?

by

Your theme’s text domain is defined in your Theme Header in style.css. For example: 

/*
 * Plugin Name: My Plugin
 * Author: Otto
 * Text Domain: my-plugin
 */

The text domain should match your theme’s ‘slug’ (ie. the name of the folder where your theme is stored).

Read more: https://codex.wordpress.org/I18n_for_WordPress_Developers#Text_Domains