* No Official List: There's no official list or database tracking the knowledge of every single word in the English language by every speaker.
* Subjectivity: "Unknown" is subjective. A word that's common to a scientist might be unfamiliar to a child. Even within a single person, knowledge of words changes over time.
* Rare vs. Unknown: Some words are extremely rare, but still have specific meanings or are used in specialized fields. These words might be considered "unknown" to most people, but they aren't truly unknown.
However, we can explore some candidates:
* Words from Old English: Many words from Old English have fallen out of common usage, like "frec" (bold) or "sceadu" (shadow).
* Technical Jargon: Words specific to a profession, like "pneumonoultramicroscopicsilicovolcanoconiosis" (a lung disease caused by inhaling very fine silica dust), are likely unknown to most.
* Neologisms: Newly coined words are often unknown until they gain traction, although these words are usually less common than older, established words.
Instead of seeking the "most unknown" word, consider the fascinating diversity of the English language and the many words waiting to be discovered!