Question

why does Gawain wear the green girdle?

Answer 1

If this is from Sir Gawain and the Green Knight than it is as follows. He wears the girdle as a reminder of his failure. As a knight he is sworn to be honest. When his host ask him to share anything he had earned that day, Gawain only gives him a kiss. This was dishonest as on that day the lady of the castle gave him the girdle. So to remind him of his dishonesty Gawain wears the girdle.