Why is the recorder called "Blockflöte" ('block flute) in German (Kathrin Härtel - recorder)

In this video you will learn where the recorder gets its German name "block flute" from.
Kathrin Härtel
soprano recorder (Fehr)
alto recorder (Fehr)
tenor recorder (Küng)
bass recorder (Yamaha)
sopranino recorder (Moeck)
Garklein recorder (Küng)
february 2021
/ kathrinhaertel