Wikipedia
Polterabend
Polterabend is a German wedding custom in which on the night before the wedding the guests break porcelain to bring luck to the couple's marriage. The belief in the effectiveness of this custom is expressed by the old adage: "Shards bring luck" (German: Scherben bringen Glück). The expression is derived from a time when the word " shard" referred to the unbroken clay pots of pottery makers, and not just the broken pieces. It was said that a full jar was a lucky thing to have, therefore the expression "shards bring luck".