I have heard this word before, and I find it fun to say. What a surprise to come across it in “The Lottery Ticket” in The Complete Casebook of Herlock Sholmes.

Perspicacity – the quality of having a ready insight to things, shrewdness

Usage: “After that amazing example of my friend’s perspicacity, nothing could shake my faith in him.”

Perhaps it is no big surprise after all that Jotson uses perspicacity to describe Sholmes. Maybe I should be more surprised that he didn’t use it ’til the last case in 1917.