Codenames are useful.
Whenever we develop software we invent names. Tons of names. VCS repository names, directory names, executable names, package names, class names, function names, configuration file names, database names, usernames. The list goes on.
A natural impulse is to use your product’s name in these names. After all, if you are developing X it makes sense to name things after X.
The problem is that most of the time we don’t know how the project will turn out: the product might (and probably will) change its the target audience, format and may metamorphose completely.
You can guess what happens in this case: public-facing identifiers will be changed quickly, but internal ones will linger: the ones that are easy to change will be changed eventually, the ones that are hard will get stuck.
Now imagine the public name changing several times over the lifetime of the project.
The codebase will accrete all names used by the product in past. From time to time a heroic effort will be applied to clean the old cruft, as it becomes harder and harder to explain to new team members that X, Y, Z and W are actually the same thing. It will mostly succeed, except that one place that requires somebody to spend an hour in a SaaS console somewhere… However there is a backlog of features, so let’s postpone it to another day…
Changing identifiers is a huge waste of time. Use codenames instead.
Codename is an internal techincal identifier. It is guarded from marketing. It is not allowed to escape to the public. It is stable. It is used everywhere where internal identifiers are needed, starting from the name of VCS repository.
Use codenames as much as you can. Don’t leak them to the users though.
P.S: If you develop desktop software, more details of your software leak to the users: configuration files or main executables should be named after marketing name. The life is much easier for SaaS or mobile apps: user-facing domains, UIs, marketplace entries and APIs have to use marketing names, everything else is hidden from the users and should use the codename.