Have you ever thought about why fast means quick and at the same time means to immobilize? When a word or phrase means its opposite as well, it is called a contronym. Slang employs this kind of inversion of meaning, take for instance the word ‘sick’ or ‘wicked’ now used to convey something awesome or cool.
Here’s a list of contronyms.
Check out this usage of the word:
Sometimes, just to heighten the confusion, the same word ends up with contradictory meanings. This kind of word is called a contronym. Sanction, for instance, can either signify permission to do something or a measure forbidding it to be done. Cleave can mean cut in half or stick together. A sanguine person is either hotheaded and bloodthirsty or calm and cheerful. Something that is fast is either stuck firmly or moving quickly.— Bill Bryson, The Mother Tongue, 1990