坦白
tǎnbái · HSK 7
frank
坦 flat/level + 白 white/clear = laying things out flat and white, hiding nothing = frank
坦 means flat or level (as in even ground) and 白 means white or clear. Putting your words out flat and white leaves no dark corners, so 坦白 is to be candid and confess openly.
白 — pictograph; resembles 日 (sun) with a stroke on top
白 is generally considered a pictograph, traditionally explained as depicting the sun rising with a ray of light above it, hence the meaning 'white' or 'bright.' Some scholars instead see it as a drawing of a thumbnail or an acorn. From 'bright' it extended to 'clear,' 'plain,' and 'to state plainly.'