The form of Latin S arises 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 now while in the epigraphy of Western Greek alphabets, as https://s39753.suomiblog.com/a-secret-weapon-for-bud-naked-mushrooms-47020980