Picture judging as aiming. You look at something and land on a conclusion. The mis- part says the landing was off target. What you land on may be a person's character, or it may be a number: how far, how fast, how long.
可以想成「下判斷」像是朝一個目標丟出去。judge 是丟，mis- 是丟歪了。歪掉的東西可能是對一個人的看法，也可能是對距離、速度、時間的估算。兩種用法的畫面其實同一個：你已經下了結論，只是結論落在錯的位置上。
From the word’s history
Recorded as mis- + judge: the prefix mis- marks an action done wrongly, and judge is the action itself.
來源記錄為 mis- 加 judge。mis- 標示「這個動作做歪了」，judge 就是那個動作本身，所以整個字的重量都落在「歪掉的判斷」上。
Wiktionary entry supplied in packet (source_ref kaikki:3f6f69a190036ae4:1495233971:7442), etymology_text: From mis- + judge.
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