Pe is usually assumed to come from a pictogram of a mouth (in hebrew pe; in arabic,fah).
Rashi comments that what differentiates man from animals is the ability to articulate intelligent speech. The ability to speak brings man to the top of the classification of the four categories of existence:
The pe stands for pe, mouth, the organ of the word. God created man and "breathed into his nostrils the breath of life, and man became a living being". (Genesis 2:7)
The shape of pe is a kaf with a yod inside of it. This represents the spiritual spark of the neshama, soul, contained inside the physical body. With words and silence we can communicate the essence of our soul and existence. This requires that the inner and outer life match - that the physical existence is fully aligned manifesting the spiritual intentions of the soul within it.
As it says in the Talmud: "Don't say one thing with the mouth and another with the hearth". (source: Baba Metziah)
Below you can see the movie of me producing the big clay prototype of a hebrew letter. The prototype will be used to design a jewel