The form of Latin S occurs from Greek Σ by dropping one out from the four strokes of that letter. The (angular) S-shape made up of a few strokes existed being a variant with the 4-stroke letter Σ by now during the epigraphy of Western Greek alphabets, as well as https://keegancwrpf.uzblog.net/not-known-facts-about-bud-naked-45361677