A good way to hold this word is to take its two parts apart. Flash is something catching light all at once, and point is the exact spot on a scale. Put together, one picture covers the whole entry: the point at which a thing that has been warming quietly finally lights. In a laboratory that point is a temperature, written on the side of a can of oil. Moved onto human life, the same picture describes a place that has been tense for years and needs only a spark, and it describes the second in an evening when the shouting finally starts. In every use, nothing is burning yet a moment before, and everything is a moment after.
From the word’s history
Wiktionary gives the make-up of the word plainly: flashpoint is from flash plus point. The packet says nothing about which use came first, so no order is claimed here.
Wiktionary 只記了這個字的組成：flashpoint 由 flash 加 point 而來。證據沒有說哪個用法先出現，所以這裡不做先後的推論。
packet evidence: Wiktionary etymology_text for flashpoint (source_ref kaikki:3f6f69a190036ae4:1251446593:1731)
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