If that was the exact phraseology, "papa" is the latest ATIS they've copied. (ATIS being a continuous broadcast of recorded aeronautical information, updated every half hour, or in case of a major change).
Listen to arrival ATIS Heathrow, and, at the very end, note the instruction to inform Heathrow on first contact.
Similarly, here's departure ATIS at JFK with similar instruction in the last line:
KJFK JFK ATIS INFO F 0251Z. 32004KT 10SM SCT140 BKN170 27/22 A3012
(THREE ZERO ONE TWO). APPROACH IN USE ILS RY 4R, RNAV Y RY 4L. DEPG RY
4L. NOTAMS... ILS RWY 22R OTS, RY 4L GS OTS. HAZD WX INFO FOR NY METRO
AREA AVBL ON FSS. SWAP IN EFFECT EXPECT REROUTES. BIRD ACTIVITY
VICINITY ARPT. NUM CRANES OPERATING AT JFK. READBACK ALL RWY HOLD
SHORT INSTRUCTIONS. ...ADVS YOU HAVE INFO F.