What does "cracker" mean in these passages from The Ferryman by Jez Butterworth:
QUINN. Where’s Michael?
CAITLIN. Flat on his cracker in bed.
MICHAEL. Morning, Tom Kettle. Where’s m’da?
CAITLIN. Out in the black barn. Killing the goose.
MICHAEL. I’m s’posed to be killing the goose!
CAITLIN. Not flat on your cracker in bed you’re not. It’s gone six.