"Police" is not an acronym. It isn't short for anything.
According to "Allexperts.com":
The word 'police' stems from the Greek word 'politeia' meaning, state, administration, government.
In Chaucer's Canterbury Tales we find the word 'policie' meaning organized government, civil administration. Later in about 1589 we find the French word 'policer' meaning to keep order. The first recorded use in English of 'police' in specific reference to those concerned with enforcing the law and maintaining public order is found in about 1730 in Scotland.
Police
Woman Police Constable
MPO stand for Military Police Officers.
The Police Department is usually abbreviated PD.
It stands for criminal investigating police officer.
Of course they are - Do you think police have to stand on trains?
International Police
Australian Federal Police
Royal Canadian Mounted Police
Police Service of Northern Ireland.
REPT is an abbreviation for Report.
MP- Military Police