Whilst you can not link tenants, you can add one or more custom domains into a tenant. When you create a new tenant, it will always have a abc.onmicrosoft.com tenant domain where abc is your own identifier, however if you own abc.com, you can add this as a custom domain. Log into the Office admin portal, and go to Setup -> Domains and tehn click Add Domain. You can add abc.com as a custom domain. You will need to verify you own the domain, so Azure will give you a TXT record for you to add to the DNS for the domain, and in the background, check for this record to verify the domain.
Once verified, you can add users using any of the domains in your tenant, so you can add [email protected] and/or [email protected]. If your abc.com email is hosted elsewhere currently, you will need to migrate the mailboxes to O365 from your current Exchange Server, and also set the correct MX records to point to O365 email.
From your desciption, your original domain is NOT a tenant, just a hosted email service from GoDaddy, so moving the domain to O365 should not be a problem, and GoDaddy should be able to help with this.