全然
ぜんぜん · zenzen · JLPT N4 · adverb
not at all
全然 = whole (全) + so/thus (然): wholly so, or with a negative, not at all
全 means whole and 然 means in that way, so the word says entirely so. Paired with a negative verb (全然わからない) it flips to not at all. Sound hook: zen-zen is the same syllable twice, a doubled zero — zero, zero, none whatsoever.
全 — enter 入 on top + jade 玉
Originally written as 入 (enter) over 玉 (jade), depicting a complete, unflawed piece of jade kept in storage. From this image of a perfect jade came the meanings 'whole,' 'complete,' and 'entire.' The top component is sometimes written as 人.