It is tomcat, definitely, in the second line, not hangover (Kater is used for both in German)

The song is about a (tom)cat that wonders why humans do kiss.

The last part, about meditating on the roof top, makes more sense for a cat than a human ...


Jünger/disciples: Jünger is used in that meaning e.g. for Jesus' twelve apostel.

Or for firefighters - "Florians-Jünger" (as Saint Florian is the saint who protects houses from fire).