The form of Latin S occurs from Greek Σ by dropping just one out of 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://rafaelaulzo.onzeblog.com/31315121/s-no-further-a-mystery