The shape of Latin S arises from Greek Σ by dropping one particular out with the 4 strokes of that letter. The (angular) S-condition made up of a few strokes existed to be a variant of the 4-stroke letter Σ already within the epigraphy of Western Greek alphabets, along with https://cashzsjao.techionblog.com/31319156/s-no-further-a-mystery