The word cuff has two main meanings:

1. The part of a sleeve that wraps around your wrist. When you roll up your shirt cuffs on a hot day, you're folding back that fabric at the end of each sleeve. Dress shirts often have button cuffs that fasten at the wrist, while sweater cuffs are usually stretchy ribbed fabric that hugs your arm. The cuffs on pants work the same way, circling your ankle at the bottom of each leg.
2. To put someone in handcuffs, the metal restraints police use. When police cuff a suspect, they're putting handcuffs on them. And if you speak off the cuff, you're talking without preparation, as if you jotted quick notes on your shirt cuff.