pap (n.1) Look up pap at Dictionary.com
"soft food for infants," late 14c., from Old French pape "watered gruel," from Latin pappa, a widespread word in children's language for "food" (Middle High German and Dutch pap, German Pappe, Spanish, Portuguese papa, Italian pappa), imitative of an infant's noise when hungry; possibly associated with pap (n.2). Meaning "over-simplified idea" first recorded 1540s.
pap (n.2) Look up pap at Dictionary.com
"nipple of a woman's breast," c.1200, first attested in Northern and Midlands writing, probably from a Scandinavian source (not recorded in Old Norse, but compare dialectal Swedish pappe), from PIE imitative root *pap- "to swell" (cognates: Latin papilla "nipple," papula "a swelling, pimple;" Lithuanian papas "nipple").
pap (n.3) Look up pap at Dictionary.com
"older man," 1844, shortening of papa.