You're thinking of the "
docker.io" package (the containerisation software) .. it's NOT installed in Peppermint by default (though it is available in the repos), and AFAIK it's not installed in Ubuntu by default either.
The package "docker" is just:-
Docker is a docking application (WindowMaker dock app) which acts as a system
tray for any desktop environment, allowing you to have a system tray without
running the KDE/GNOME panel Docker was designed to work with Openbox 2, but it
should work fine in any window manager.
But again "docker" is NOT installed in Peppermint by default either (but is available in the repos).