An excerpt from this Wikipedia page:
Santiano is a German band from the northern region of Schleswig-Holstein, Germany, whose genres include Irish folk, sea shanty, and schlager music. The name Santiano is taken from the Hugues Aufray song of the same name. They topped the German, Austrian, and Swiss charts in the mid 2010s.
One of their songs, Mädchen von Haithabu, sounds very similar melodically to the linked section of Michael Sweeney's Celtic Air and Dance No. 2, a composition for which I played percussion in my high school concert band. The section is based on the traditional Scottish song Tha Mi Sgith (Scottish, not Irish, nor German).
It seems that Santiano wrote Mädchen von Haithabu themselves, but is it likely that they, like Michael Sweeney, were inspired by Tha Mi Sgith?
Edit: As pointed out by the accepted answer, I made a mistake. Both songs are based off of Star of the County Down, not Tha Mi Sgith. I've played far too many Celtic songs in concert band :)