From this informative page:
The German name for Good Friday (Karfreitag) comes from the Old High German form kara, which has the same meaning as the English word 'care'. This gives the meaning of 'Sorrowful Friday to the day when Christians remember the crucifixion of Jesus Christ. It is also known as 'Quiet Friday' (Stiller Freitag) for obvious reasons. On this very solemn day no church bells are rung in Roman Catholic churches. Some children believe that the bells are sent to Rome at this special time to be consecrated. Consequently the male members of the communities make up for the lack of noise with the 'Good Friday rattles' - in appearance rather like football rattle - which not only provide them with pleasurable task of making a lot of noise but also summon the villagers church services. In Swabia a loud-mouthed person is rebuked with saying: 'You have a mouth like a Good Friday rattle' (Dui hot e Meul wie e Karfreitigrätsch).
In former times there were far more restrictions on individual behaviour on this day of mourning than there are today. The drinking of alcohol was strictly forbidden in order to bring to mind the fact that Jesus Christ was thirsty whilst on the Cross. No one was allowed to kill an animal and the blacksmith was not allowed to use either hammer or nails, since these were employed in the Crucifixion. In some homes the crockery which had been specially polished during the Green Thursday spring clean was kept covered up in baskets until Easter Saturday, since it was considered unfitting for anything sparkling to be on view on Good Friday.There are special church services on Good Friday, some lasting for three hours, and Bach's St. Matthew's Passion is performed in many churches. Passion Plays used to be popular on Good Friday but are rarely performed today. The Passion Play in the Eifel mountains was banned around the year 1800, because it was considered to have become too worldly and to be too distracting. Many families eat the familiar Lenten food on Good Friday, choosing fish in preference to eggs or meat, and in some areas the bread eaten on Good Friday has the sign of the cross marked on the crust. Twigs from the sloe tree and buchthorn are sometimes brought into the house as an Easter decoration, reminding the householders of the crown of thorns which Jesus Christ was made to wear. Furthermore, a symbol of new life and future growth is to be found in the blossoms the branches bear, in the same way as Jesus Christ in his resurrection was the first fruit of believers.