Question: The Messerschmitt 109TL was an alternative design proposed as a backup for a fighter version of a plane nicknamed what? 
Sentence (from "Messerschmitt Me 262"): The Messerschmitt Me 262, nicknamed Schwalbe (German: "Swallow") in fighter versions, or Sturmvogel (German: "Storm Bird") in fighter-bomber versions, was the world's first operational jet-powered fighter aircraft.
Relevant evidence: Yes