dad (n.)

"father," 1680s, from French papa, from Latin papa, originally a reduplicated child's word, similar to Greek pappa (vocative) "o father," pappas "father," pappos "grandfather." The native word is daddy; according to OED the first use of papa was in courtly speech, as a continental affectation, and it was not used by common folk until late 18c.

"father," by 1851, a nursery or provincial abbreviation of dad.