Symptoms
When your cPanel account has been configured to use a language other than English, and you switch the account to use English, the Calendar, Address Book, and Shared Address Book names and descriptions under the Secure SSL/TLS URLs section of the Calendar and Contacts page remain in the original language.
Workaround
The text in this section pulls its values from the Horde database for the main cPanel account. To switch the values back to English, access the main account's email from the Email Accounts page, then update the corresponding names and descriptions for the Calendar, Address Book, and Shared Address Book in Horde.