4. (American.)—Also bubby. A term of affection applied to a little boy.
[Said to have originated in Pennsylvania from the German Bube.]
Likewise used figuratively as a familiar mode of address.
1872. S. Clemens (‘Mark Twain’), Roughing It. The cayote turns
smiles blandly upon him once more, and with a something about it
which seems to say: ‘Well, I shall have to tear myself away from
you, bub—business is business, and it will not do for me to be
fooling along this way all day.’
1888. San Francisco Weekly Examiner. When she was ready to go home,
she did so without carriage or baby. Shortly after bubby kicked up
high jinks, and the joker clerk was sent for to take him away.