See it as 木 (wood) + 官 (official): the tree is the material, the official is the phonetic - simple, picturable.
Pin on one cultural hook: imagine 納棺の儀 (the encoffining rite) - cedar scent, incense, lacquered black with gold clasps, distant temple bells - or Shoulder-a-Coffin Kuro passing rows of haniwa on a Kofun mound; the sight, smell, and the kan! make the character unforgettable.