Definition of "coot"

Once more he thought aloud. / "Tom wouldn't lie to me, so it wasn't gin. Now, I wonder. I wonder if that old coot has got what they call 'delusions of grandeur'?"

1918, The Saturday Evening Post, volume 190, numbers 35-43, page 109

Your clerks would come in and see you aswingin' and aswayin' there and one of them would say: "Well, the old coot's hung himself!"

1926, Don Marquis, The Old Soak: A Comedy in Three Acts, volume 2, page 84

“You'll be able now to give it as your considered opinion that [Wilbert Cream] is as loony as a coot, Sir Roderick.” A pause ensued during which [the psychiatrist] appeared to be weighing this, possibly thinking back to coots he had met in the course of his professional career and trying to estimate their dippiness as compared with that of W. Cream.

1960, P. G. Wodehouse, Jeeves in the Offing, chapter VII