They’re usually just complicated acronyms. Mice is is the identities service (I believe the I is for identities), and Shelby is the accounts service. Nothing top secret here!
These are references to microservices which handle certain import, export, and lookup functionality. ConfigurationHub (sp-config) coordinates actions across a variety of microservices, as you’d expect.
Beyond this, you may also see these names in private APIs behind certain user interfaces for newly created functionality too. Often these launch before a new beta APIs are launched. The private APIs allow our developers to iterate in an early access fashion without having to be locked into a versioned API, even if it is beta.