With all the talk of garter tossing, I looked this up ...
Tossing the wedding garter is an old time held tradition. It is said that in the days gone past, the bride and groom had to show proof of their wedding consummation. In order for it to be proven, it was common tradition to have people like family and friends come into the room with the couple. The "witnesses" would obtain the garter as "proof" of the consummation. Also having any article of the under garments was considered to be good luck so sometimes things would get out of hand in the newly wed's bedroom as crazed onlookers snatched at clothing to get for good luck. This was not appreciated much by the bride nor many grooms, hence the groom started tossing the garter out so that no one would need to obtain it themselves.
( How barbaric this sounds! glad things have changed since then)