I am trying to find a word which describes someone who is both old and wise. I would like the word to describe someone who is extremely frail and infirm. It might also have the connotation that their counsel is odd or hard to follow, even if it is sound advice.
The closest word I can think of is “sage”, which seems to connote someone who is both old and wise.
In certain contexts, it might also be possible to use “patriarch” or “elder”, which both imply wisdom or age, but these words add some political connotations that may or may not be desirable.
I’m not sure if there exists a word that includes quirkiness, too. If you don’t mind using semi-proper names (in a somewhat more metaphorical sense), you could use “einstein”, “oz”, or “yoda”. These can be probably be used as common nouns, but they may be too strongly tied with the original individuals the words come from.