pillow toy

A pillow toy is another term for a self pleasuring device (more than likely to be a dildo) that is hidden underneath a pillow.

Me: "Dude I was cleaning my parents' room for money and when I was making their bed, I found a pillow toy."
Friend: "Haha. Really?"

unchain your pillow

Unchaining your pillow can be used in many different ways

Describing how beautifully poetic something is

or

to talk around NSFW topics

Example 1:

This poem was so beautiful, it unchained your pillow

Example 2:

I want to unchain your pillow later?