The ninth trump has a documented change of identity, and it is one of the few places where a modern reading is demonstrably a replacement rather than an addition.
In several fifteenth-century Italian decks the figure is Time: an old man carrying an hourglass, sometimes with wings, sometimes hunched, occasionally titled Il Vecchio, the old man. That is a standard Renaissance personification and it belongs with the triumphal sequence, where Time defeats Fame. In the French pattern the hourglass has become a lantern and the title is L'Hermite, the hermit. The change turns a card about the passage of time into a card about withdrawal and search, and everything modern readers do with it follows from the lantern rather than the glass.
Both objects are still present in practice, if only implicitly. The card is read for solitude, for deliberate withdrawal from company in order to think, for teaching that must be sought out rather than offered, and for the recognition that some questions cannot be answered at speed. Underneath that sits the older sense: that the thing being asked about will be settled by duration, and that the querent's part in it is to wait out a period they cannot shorten.
The occult layer arrives late, as everywhere. The Golden Dawn assigned the card the letter Yod, the sign Virgo, and the twentieth path from Chesed to Tiphareth. Yod is the smallest letter, the point from which the others are formed, and it fits a card about a single figure carrying a single light rather better than it fits an old man with an hourglass, which is a reasonable indication of which version of the card the order was looking at.