Hold up one hand and look at the last small piece of a finger. That piece reaches first, touches first, and feels most. It is also the point of you: past it there is only air. One way to hold fingertip is as that reaching, feeling far end. Everything else the word does comes from one of those two facts. Because it reaches first, whatever is already under it needs no searching. Because it is the point of a person, going out to it means going all the way. And because it touches so lightly, a touch with it is the smallest push there is.
From the word’s history
A compound of finger and tip, the same way English makes tiptoe and toetip.
由 finger（手指）＋ tip（尖端）合成，跟 tiptoe（腳尖）、toetip 是同一種造字方式，字面意思就是今天的核心畫面。
Wiktionary entry supplied in packet (kaikki:3f6f69a190036ae4:714306488), etymology_text: From finger + tip. Compare tiptoe and toetip.
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