Elsewhere in this atlas the Latin P's sound is traced to Phoenician pe, meaning mouth, by way of Greek pi. The graphic history is less direct than that phrase suggests. Classical Athenian Greek wrote pi with two short legs beneath a flat top, the angular letter still used in Greek today, but the western Greek alphabets of southern Italy and Sicily, the ones Etruscan and then Rome actually borrowed their letters from, used an older, more rounded regional variant of pi with a single curved bow, closer in outline to a modern P than to the Athenian letter.
Roman P descends from that western form rather than from the pi familiar from classical Athenian inscriptions, which is why the Latin and Greek letters, despite sharing a common Phoenician ancestor and occupying the same position in each alphabet, look so different from one another. The Roman capital P, a vertical stroke with a bow at the top, was fixed by the classical period and has changed little since; the lowercase p extended the stroke into a descender below the line while keeping the bow, a straightforward adaptation fixed in medieval cursive and carried into the Carolingian minuscule. P has no Roman numeral value and no ancient numerological tradition attached to its shape, unlike its Hebrew and Greek counterparts covered elsewhere in this atlas.