No, poiniest is correct. i.e., if you are one of many poindexters, you are the dexter that is poiniest.
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“The Poindexter family name is a legacy Britain’s Norman past. It comes from the Old French “poing destre,” meaning “right fist;” and as such is thought to have originally been some kind of nickname. [1] [2]
However, another source disagrees with this generally accepted origin. “This name does not signify ‘ the right hand,’ as might easily be imagined, but is an old Norman name, signifying Spur the Steed, and analogous to Hotspur. It comes from two old words, which Wace often uses in the Roman de Rou; the first meaning ‘ to spur,’from the Latin pungo; the second, ‘a steed or courser,’ in French destrier, Ital. destriere.” [3]”
So poin is either “fist” or “spur”. Dexter is either “right” or “steed”. I would go with the first version, making you the best fist on the right. Kinda like a BLM symbol, only for good.
I get your point.