A tilde is a grammatical thingy -- Thingy -- That looks like so: ~

... I have no idea what it does because I only pretend to be smart.

Now for the story. :|

Once upon a time there were twin sisters named Polly and Esther. They wore hideous, inexpensive, tacky dresses and went dancing. Naturally, they sweat up a storm and stank up whatever club they were at. The pair became so infamous that eventually people stopped referring to the fiber by its scientific name and simply called it polyester after the two vapid, disgusting, unhygienic girls.

The end.