-Xdock is a Mac OS X flag for setting app name and icon in Mac OS X dock. It used by org.nanode.launcher.Launcher to improve user experience.
-Xdock originally supported multiple arguments in one setting, as "-Xdock:name=foo:icon=foo.icns". Apple has announced this multiple-argument use is deprecated and should be split into two separate arguments, like "-Xdock:name=foo -Xdock:icon=foo.icns".
This is Apple issue #2782802.