According to legend, pretzels were invented hundreds of years ago as a treat for choir boys during Lent. I guess treats were normally given as a sort of Behavior Modification technique to keep the boys' behavior under control, but during the season before Easter all Christians fasted and sweets were not allowed.
In one monastery someone had the idea of creating a sort of bread that resembled arms crossed over the breast, the usual position for praying in those days. The crisp and salty breads were tasty enough so the choir boys would consider them a reward worth behaving for, but still had the spiritual aspect of reminding them to pray.
The pretzels were so good they were soon made by Christians everywhere as a lenten food.
I don't know if the story of their origin is true or not, but in some churches and families pretzels are still given to children today as a reminder to pray during the 40 days preceding Easter.