Yes, Maggie Chickens -- Roosters, hens, chickens -- all chooks.
For little kids -- "Chookies". I've thought it comes from the way they're called -- as in "Here chook, chook, chook" which in turn may come from the sounds they make.
Must look it up.
Some signs around Melbourne offer "Hot Chooks" as in roasted ones.
Cheers, Joy