A separate footrest for a chair is known as an ottoman, hassock or pouffe.
From the en.wikipedia.org
I shake my head, move the hassock over, press my cheek to hers.
From the well.blogs.nytimes.com
The camel-hide hassock, the bouquet of used plastic flowers, and the two secondhand bedspreads were quickly snapped up.
From the time.com
Elsewhere there are a hassock-size cylinder of cast black glass by Roni Horn and a large, gnarly tree limb covered by gold glass beads by Liza Lou.
From the nytimes.com
More examples
Ottoman: thick cushion used as a seat
A cushion for kneeling on (as when praying in church)
Tuffet, pouffe or hassock are all terms for a piece of furniture used as a footstool or low seat. It is distinguished from a stool by being completely covered in fabric so that no legs are visible. ...
Hassocks is a large village and civil parish in the Mid Sussex district of West Sussex, England. Its name is believed to derive from the tufts of grass found in the surrounding fields.
To dream of a hassock, forebodes the yielding of your power and fortune to another. If a woman dreams of a hassock, she should cultivate spirit and independence.