It is made from the cloth used to swaddle a baby boy at his bris milah, uniting the communal world of the synagogue with the individual's own life cycle.
It is an extremely joyous occasion, and its main purpose is to instill a love and enthusiasm for shul and Judaism within the child.
The custom gradually developed into the one that is practiced today by German Jews: At a baby's circumcision, the mohel places a long swatch of white cloth – the wimpel – under the pillow.
Afterwards, the wimpel is beautifully decorated – it can be either painted or embroidered – with the child's name, date of birth, and the Hebrew phrase which states “Just like he entered the [covenant of] circumcision, so too he should [the covenant of] Torah, marriage, and good deeds.” Some mothers do the artwork themselves; others retain the services of “wimpel professionals,” e.g., men or women who do this as a side job or hobby.
The cloth is cleaned, cut into strips and sewn into a sash measuring six or seven inches wide and ten or twelve feet long.
Rabbi Shimon Schwab, Rav of Khal Adath Yeshurun synagogue in Washington Heights, New York, which revived the custom among the younger generation of Yekke congregants, suggested that perhaps the source of the wimpel custom was to avoid knotting and unknotting a tie around the Torah on Shabbat (see the 39 categories of activity prohibited on the Sabbath).
On that first Shabbat that the wimpel is presented and used, the child's family makes a kiddush in honor of their son's entering into a life of Torah.
A boy's wimpel would then be placed on the Torah on other special occasions in his life, such as his Bar Mitzvah, Aufruf, and other important family events.