what is a hungertuch? I know it is German, but what is it ?

If fasting is done in a visible and organized way, a “hunger veil” may be introduced. First mentioned in the ninth century, this large cloth veil (das Hungertuch in German) reminded the congregation's members of the Lenten theme of fasting and self-sacrifice.

Proposed translation:

Lenten cloth, Lenten veil

It is a kind of "towel", which should be put on the main altar in the Catholic church during the time before Easter. You can see (for example) some prints of suffering of Jesus Christ/ Passion of Christ on it

a veil to cover the icons or mostly images of the Christ during the

lenting season. in Catholic churches.