The thirteenth trump is untitled in most French printings. The card face carries the number and no name, which is unusual enough in a pattern that names everything else to be worth explaining. The most economical explanation is superstition: printers did not care to put the word on a card people would handle daily, and the number thirteen was already doing the work.
The image beneath the silence is agricultural and blunt. A skeleton with a scythe mows a field in which heads, hands and feet are still growing, and one of the heads is crowned. The point is unmistakable and it is a medieval commonplace, the same point made by every danse macabre painted on a charnel-house wall in the same centuries: everybody, including the king. This is not a card about transformation. It is a card about mortality, in a period that had excellent reasons to think about mortality often.
The modern convention that Death "almost never means physical death" in a reading is a twentieth-century interpretive rule, not an old one, and it is worth knowing that it is a rule readers agreed on rather than a fact about the card. It exists for good practical reasons, a reader telling a stranger they are about to die is doing harm and is usually wrong, but it should be described as an ethic of practice rather than as the card's meaning.
The Golden Dawn assigned the card the letter Nun, the sign Scorpio, and the twenty-fourth path from Tiphareth to Netzach. Nun is a fish, and its association with life in the depths is often used to soften the card; that softening, too, is a nineteenth-century contribution.