The shape of Latin S arises from Greek Σ by dropping just one out of your 4 strokes of that letter. The (angular) S-condition made up of a few strokes existed to be a variant of the four-stroke letter Σ currently while in the epigraphy of Western Greek alphabets, as https://bud-naked-vape65309.jts-blog.com/30525534/the-2-minute-rule-for-bud-naked-concentrate