The letter "P" is the sixteenth letter of the modern Latin alphabet. Its origins trace back to the Semitic letter "pe," which likely derived from an earlier sign meaning "mouth." The Greeks adapted this form into the letter "pi" (Π). The Latin alphabet later borrowed a rounded form of the letter from the Etruscans, which evolved into the "P" we recognize today. This letter has been part of the Latin alphabet and English writing system for many centuries, evolving from ancient alphabets used thousands of years ago. The exact time of its original creation is ancient and not pinned to a specific date, but it has been in use at least since the time of the Greeks and the Etruscans before becoming part of the Latin alphabet.
If by "P" you meant "pi" (π), the mathematical constant, the Greek letter π was first used as a symbol for this constant by William Jones in 1706 and became standard mathematical notation roughly 30 years later.
If you clarify which "P" you meant (letter, mathematical pi, or something else), I can provide more specific details.
