Removing third-party domains
If you no longer want a third-party domain associated with your online store, then you can remove it from your Shopify admin. If the third-party domain is your primary domain, then you need to Change your primary domain before you can remove the third-party domain.
After you remove a third-party domain, you can change your DNS settings in your third-party domain provider account to point the domain to another website.
If you want to use the third-party domain for your Shopify store again after you remove it, then you can reconnect the domain in your Shopify admin.