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 3 strokes existed for a variant of your 4-stroke letter Σ by now in the epigraphy of Western Greek alphabets, as well as https://johnnyhaoes.blog2freedom.com/31304157/how-bud-naked-can-save-you-time-stress-and-money