Oblivion
Etymology
From Latin oblivio, "forgetfulness," from oblivisci, "to forget." The deeper origin of oblivisci is uncertain; one longstanding suggestion links it to ob- plus levis, "smooth," as if memory were wiped smooth like an erased slate, though this is disputed. English carries both the passive sense of being forgotten and the active sense of forgetting one’s surroundings.
noun · /uh-BLIV-ee-un/
The state of being completely forgotten, or of being unaware of what surrounds you.
What it names
Either total erasure from memory — sinking into oblivion — or the condition of a person so absorbed or insensible that the world passes unnoticed.
Example
Once a household name, the inventor drifted into oblivion, his patents gathering dust in an archive no one visited.
Related idea
Obscurity means being little known or hard to notice, but still findable; oblivion is the fuller darkness of being erased or forgotten entirely.