'inmost' is a correct and usable word in written English.
You can use it to describe something that is located at the deepest or most central point or part of something. For example, "The archaeologists uncovered a secret chamber in the inmost depths of the pyramid."
Speaking, for example, of the neglect by his contemporaries of his work, Nietzsche writes: "I myself have never suffered from all this; what is necessary does not hurt me; amor fati [love of fate] is my inmost nature" (EH III CW-4).
And so, like Ishmael, he charged boldly on:and in the wild conceits that swayed me to my purpose, two and two there floated into my inmost soul, endless processions of the whale, and, mid most of them all, one grand hooded phantom, like a snow hill in the air.
Indeed, he described him as the "unsurpassed master of…laying bare the inmost core of spiritual truth".
Coleridge's operative words and phrases in his discussions of tragedy were "innate," "from within," "implicit," "the being within," "the inmost heart," "our inward nature," "internal emotions," and "retired recesses".
Schopenhauer acknowledged a connection between human feeling and music, which "restores to us all the emotions of our inmost nature, but entirely without reality and far removed from their pain".
"You may be seeing less of my inmost depths than you believe".
But a caped dynamo is a piston that powers the plot, rather than a repository of our inmost wishes.
None of us are completely decent, but for decades he brought to social intercourse the impatience of an incorrigible alcoholic, his inmost attention focussed on the next drink.
Who would have guessed, after a year of headlines about the N.S.A. and about the porousness of life online, that our worries on that score — not so much the political unease as a basic ontological fear that our inmost self is possibly up for grabs — would be best enshrined in a weird little romance by the man who made "Being John Malkovich" and "Where the Wild Things Are"?
At another time, it hides itself in the inmost recess of the heart, or coils around it like a serpent; now it fixes upon the lungs; now upon the kidneys, upon the liver, the bladder, the pancreas, the intestines of the skin.
"This is the first time we are revealing it to people outside our inmost circle of three," Bonnefoy said.
