Isn't it
A little bit of cu-cum
I come, you come,
A little bit of cu-cum-ber...? I heard it done that way on the BBC Light Programme by Billy Cotton & his band (or some other of that ilk); in those days it wouldn't have been thought of as "unsuitable" because of the sheltered lives led by The Powers That Were on the wireless. But it wouldn't be our 'Arry if it didn't sound smutty, would it?

Steve