 The original Semitic letter may have been inspired by an Egyptian hieroglyph for "tp", "head".It was used for by Semites because in their language, the word for "head" was "rêš" (also the name of the letter).It developed into Greek 'Ρ' ("rhô") and Latin R.

The descending diagonal stroke develops as a graphic variant in some Western Greek alphabets (writing "rho" as ), but it was not adopted in most Old Italic alphabets; most Old Italic alphabets show variants of their "rho" between a "P" and a "D" shape, but without the Western Greek descending stroke.