Two unusual usages in The Mansion, as far as I can tell. Page numbers are from the Library of America edition.
So they would reach that side by side anyway—the vast dim home-made columned loom of her father’s dream, nightmare, monstrous hope or terrified placatement, whichever it was, whatever it had been… (chap. 15, p. 652)
It’s clear from context that placatement is a near-synonym for placation, but an entry for placatement does not appear in my dictionaries.
He didn’t know why; he could not have said that, having had to do without privacy for thirty-eight years, he now wanted, intended to savor, every minuscule of it which freedom entitled him to… (chap. 17, p. 692)
Minuscule is certainly a legitimate noun, in the senses of “script” or “small letter.” But William Faulkner’s use of it to mean a tiny portion is perhaps unique, and quite tasty therefore.