TL – Teelöffel (teaspoon, unit of measurement)

TL is the abbreviation for the unit teaspoon in German, the way ts is the abbreviation for teaspoon in English.

Yeah, I also didn't get the 'teaspoon' reference.

German word for teaspoon per googling it on the bing: Teelöffel

Seems like the obvious abbreviation for that is TL, so it's a joke on cross-language abbreviation collision.