What is the origin of ゟ (より)? `` is a digraph that is read . Where does it originate from? Is it a ligature, like `& <- et`, or German `ß <- ſs -> ss`? (Wikipedia claims this, citing no source.) Also, if it _is_ a ligature, what did the ligation process look like (e.g. what are the intermediate forms between `` and ``)? Alternatively, could it be a derivative of `` or another kanji? (Another non-authoritative source which I have now lost track of claims this.)

There are quite a few old (17th century) letters on this page which use the digraph as ligature of and . For example see the fifth line from the left of the following letter, which reads .

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As @ZhenLin points out, it is not too far a stretch of your imagination that comes from joining and in vertical writing. All that is really lost is the loop of the .