Remove a subdomain
When you remove a subdomain from your store, it might have an impact on how your store is set up or how your customer finds your store. You can't remove a subdomain if it's the primary domain.
Before you remove the subdomain, verify that it isn't being used in your store to find certain pages, and that it's not the primary domain.
From your Shopify admin, go to Settings > Domains.
Click the subdomain that you want remove.
Click Delete subdomain.
Click Remove to confirm.