4 letters:
ca b, ca d, ca p, ca t

5 letters:
bogie, booky, bubby, bucky, buddy, buggy, butty, but t, ca be, ca de, ca te, ca ti, cooky, cubby, cuddy, cuppy, cutty, cut e, cut t, deque, dubby, dubey, dubie, ducky, duddy, goody, guppy, gutty, puggy, puppy, putti, putty, put e, put t, tubby, tutty

6 letters:
boogie, bookie, book e, buckey, buddie, bud he, bug he, but he, ca key, cookee, cookie, cook e, cub he, cuddie, cup he, cut he, duckie, goodie, guttae, gut he, pub he, pup he, puttee, put he, took e, tub he, tuckey, tug he

7 letters:
book he, buck he, butt he, cook he, duck he, good he, putt he, put tea, took he

8 letters:
could he, duck key, took key