hidness means secrecy; hiddenness. Lexicurio rates it Sui generis — a strength score of 88 out of 100.
Why “hidness” is a great word
HIDNESS — [Noun] The state or quality of being hidden. From Middle English hidnes, hudnesse, from Old English ġehȳdnes ("comfort, security"), equivalent to hide ("to conceal") + -ness (suffix forming abstract nouns). Unlike "secrecy," which implies an active, intentional practice, or "obscurity," which suggests a lack of clarity or prominence, hidness is the bare, ontological condition of being unseen. It is the cool damp of a moss-lined den, the patient quiet of a deer in the bracken, and the absolute dark behind a waterfall's curtain—the profound, archaic comfort of being unavailable to the world.
Etymology
From Middle English hidnes, hudnesse, from Old English ġehȳdnes (“comfort, security”), equivalent to hide + -ness.