Where does “ammattilaisurheilulaji” come from?

ammattilaisurheilulaji (Finnish) comes from Finnish ammattilainen, from Finnish lainen, from Finnish laji, from Old Swedish slagh, from Middle Low German slach, from Old Saxon slag, from Proto-West Germanic slagi, from Swedish slagg — to hit; strike; to hit, strike, throw; to hit,...

ammattilaisurheilulaji (Finnish): professional sport sport, such as golf, tennis or ice hockey, in which best athletes receive sufficient salaries or fees to make a professional career out of it