Mother Carey’s chickens, n. — Green’s Dictionary of Slang

Mother Carey’s chickens n.

[? play on orig. naut. Mother Carey’s chicken, the storm petrel, as one who enjoys controversy or actively promotes it]

two people who are sharing living quarters and the payment for them, or likewise sharing a cab.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 121: Mother Cary’s Chickens – to fare alike and pay the same.
1883		J. Greenwood Odd People in Odd Places 231: ‘I’d take it as comfortable as going to bed,’ says my friend, ‘if there was occasion,’ ‘Then here goes to make you comfortable, you confounded Mother Carey’s chicken,’ says the second mate, turning all of a sudden fierce on him.
1909		Houston Post (TX) 25 July 49/3: ‘Then this Mother Carey’s chick of the desert sits down by me’.