bub (n.) Look up bub at Dictionary.com
"a woman's breast," 1860, short for bubby.
bub (n.1) Look up bub at Dictionary.com
also bubby, familiar address for males, 1839, perhaps a variation of bud "a little boy" (1848), American English colloquial; perhaps from German bube "boy." But sometimes, along with bud, assumed to be a corruption of brother (compare buddy, bubba).
bub (n.2) Look up bub at Dictionary.com
"strong drink of any kind," especially malt liquor, 1670s, perhaps imitative of the sound of drinking.