Vague, low-level discomfort.
Vague, low-level discomfort — a diffuse sense that something is subtly wrong, without a nameable cause.
The vaguest and lowest-grade member: it denotes the absence of comfort rather than a sharp or nameable fear — “a feeling of unease came over her.” Where worry attaches to a specific problem, anxiety is anguished, nervousness is agitated and pre-event, and misgiving is a pointed doubt, unease is the word for something feeling subtly off that you can't put your finger on. It uniquely covers social awkwardness too. Quiet and pervasive — below alarm, dread, panic, or terror.
Early 14c. unese, originally “bodily discomfort” (now archaic); the “mental distress” sense is from the late 14c. Transparently un- “not” + ease.
The same physical-to-mental drift seen in worry and anxiety: from bodily discomfort to mental/emotional distress by the late 14c. No recent-generation shift is sourced.