The form 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 4-stroke letter Σ now within the epigraphy of Western Greek alphabets, as well https://raymondletiw.webbuzzfeed.com/31851092/bud-naked-exotic-fundamentals-explained