Wiedersehn is a compound noun meaning "reunion" or "seeing again." While Auf Wiedersehen (goodbye) is common, the standalone noun Wiedersehn is less frequent and carries a deeper emotional weight.
In the context of the song, it's used to express a hopeful sentiment: "Irgendwann gibt es ein Wiedersehn" (Someday there will be a reunion). This suggests a longing for a future meeting with a lost friend, making it a poignant and memorable word that resonates with themes of friendship and remembrance.
This song is a toast to a friend who isn't there anymore. The singer is the last person left in a bar at closing time. Chairs are on the tables, and the first light of morning is coming through the window, but he doesn't want to go home. He's remembering his friend, hearing their voice singing about "Freiheit und Dosenbier" (freedom and canned beer) and even carves their name into a table just to feel like they're with him.
The whole song is built around this one beautiful, sad gesture: buying one last drink for his absent friend. He says, "Die letzte Runde geht auf mich / Die letzte Runde nur für dich" (The last round is on me / The last round is just for you). He grabs an old guitar off the wall and plays their song, imagining his friend singing along somewhere. The song ends with a hopeful thought: even if we don't know what happens after life, "Irgendwann gibt es ein Wiedersehn" (Someday there will be a reunion).