Tree of Knowledge

Subject: Tree of Knowledge
Era: Present (destroyed ~20 years before Enies Lobby)
Related: Ohara Poneglyph Clover Nico Robin
Name meaning: 全知の樹 (Zenchi no Ki) — literally 'Tree of Omniscience' (全知 = omniscience/all-knowing). VIZ renders it 'Tree of Knowledge.' References the biblical Tree of the Knowledge of Good and Evil (the tree Adam & Eve ate from). Possibly modeled on Methuselah, the ~4,800-year-old bristlecone pine (one of the oldest living trees) — the in-story tree is ~5,000 years old.

The colossal tree-mounted library of Ohara — “THE TREE OF KNOWLEDGE — OHARA LIBRARY AND ARCHAEOLOGICAL RESEARCH CENTER” (Ch. 391, p. 19).

What we know

Ch. 391 (p. 14): the great tree of Ohara is shown in the flashback’s opening caption panel (“TWENTY YEARS EARLIER · WEST BLUE · OHARA”).
Ch. 391 (p. 19): captioned “THE TREE OF KNOWLEDGE — OHARA LIBRARY AND ARCHAEOLOGICAL RESEARCH CENTER” — a giant tree housing Ohara’s library and the workspace of the Archaeologists of Ohara.
Ch. 391 (pp. 19–20): the scholars, led by Professor Clover, certify the eight-year-old Robin as an archaeologist here — the institutional heart of Ohara’s archaeology.

Surface: 全知の樹 (Zenchi no Ki) = literally “Tree of Omniscience” (全知 zenchi = omniscience / all-knowing); VIZ localizes it as “Tree of Knowledge.”
Real-world reference: the biblical Tree of the Knowledge of Good and Evil (Genesis) — the tree from which Adam and Eve ate, gaining forbidden knowledge. The parallel is exact in theme: a tree of forbidden knowledge whose fruit (here, the decoded Void Century) brings catastrophe down on those who reach for it (see True History Ohara Was Killed For). Its great age (~5,000 years) and library role also evoke Methuselah, the ~4,800-year-old bristlecone pine (among the oldest living trees), and the lost Library of Alexandria.
Confidence: high. Source: One Piece Wiki Tree of Knowledge trivia (literal meaning “Tree of Omniscience” listed in the infobox).

The institutional heart of Ohara’s archaeology — the scholarly enterprise of decoding forbidden history that makes the island a Buster Call target (see True History Ohara Was Killed For). Destroyed alongside the island ~20 years before Enies Lobby.

True History Ohara Was Killed For — what the scholars decoded that got Ohara erased.
Void Century and Ancient Kingdom — the blank century the Ohara archaeologists studied.