針刺出來的那個洞
這一支就是那個動作留下的東西本身：一個小到要找才看得到、但確實穿過去的洞。
noun · B2
A very small hole in something, like the one a pin makes when it goes through; also the small wound a pin leaves in your skin.
針孔；小洞
核心畫面
Hold a pin and push the point once through a sheet of paper. Three things come from that one moment, and the word has kept all three. There is the hole, so small you have to look for it. Hold the paper up to a lamp and the hole becomes a tiny bright dot. And if the point went into your finger instead, there is the quick sting that is over in a second and leaves nothing behind. Hole, dot, sting: every use of pinprick is one of those three, kept at exactly that size.
可以想一個動作：拿一根大頭針，往一張紙上點過去。那一下同時留下三樣東西，而這個字三樣都收著了。第一是那個洞，小到要找…更多收起
可以想一個動作：拿一根大頭針，往一張紙上點過去。那一下同時留下三樣東西，而這個字三樣都收著了。第一是那個洞，小到要找才看得到。第二，把紙舉到燈前，洞就變成一個小亮點。第三，如果針點到的是手指，就會有那一下很快的刺痛，一秒就過去，什麼也沒留下。洞、點、刺，pinprick 的每個用法大致都是這三樣之一，而且都保持在針尖那個大小。From the word’s history
The source says the word is simply pin plus prick, so both parts are still visible: the tool, and the small sharp puncture it makes.
來源資料說這個字就是 pin（大頭針）加 prick（刺、刺出的小洞）組成的。兩個部分到今天都還看得見：一個是工具，一個是它刺出來的那一下。所以這個字不需要記典故，把針點在紙上的那個動作記住就夠了。
Wiktionary entries for pinprick (noun and verb), packet source_refs kaikki:3f6f69a190036ae4:1485615486:2376 and kaikki:3f6f69a190036ae4:1485617862:3376 — from pin + prick.
Three branches
舉到燈前看到的那個亮點
把紙舉到光前，洞就不再是洞，而是一個小亮點。這一支說的是大小和形狀，不是穿透。
noun · B2
A very small dot or point of something, especially of light, about as big as the mark the point of a pin would leave.
針尖大的小點
針扎皮膚的那一下
如果針點到的是手指，留下的不是洞也不是光，而是那一下很快就過去的刺痛。
noun · B2
A small problem or small piece of damage that annoys you a little but does no real harm, especially when you set it beside something much worse.
小煩惱；小刺