What semantic notions underlie "durable; to endure" (耐) with "about 3 cm", "tiny" (寸)?

Question

CUHK doesn't expound the semantic shift. Doesn't 寸 contradict 耐? Humans usually "endure" or "resist" what's hefty and strong, not objects that are "tiny" and merely "about 3 cm".

Etymologies

「耐」本作「耏」，古刑名，參見「耏」。後引伸有忍、受之義。《廣韻》：「耐，忍也。」《荀子．仲尼》：「能耐任之，則慎行此道也。」

Wiktionary has the same etymology, but I quote Yellowbridge for it's trustworthier.

Answer 1

「耐」 (Baxter-Sagart OC: /*nˤə-s/, minor punishment involving the shaving of a beard > to endure) is comprised from doubly semantic and phonetic 「而」 (/*nə/, picture of a beard, now written 「髵」) and semantic 「寸」 (picture of a hand > actions of the hand).

---

「寸」 rarely or never means inch as part of other characters - it is derived from 「又」 (picture of a hand) with an additional mark pointing to this wrist area. As a stand-alone character, this meaning originally referred to the area where the pulse is taken (Chinese medicine: 寸口). As part of other characters, it plays the same meaning role as 「又」 (if it is used for meaning, not sound). Observe, for example,

• Glyph origin of 「對」, compound of a hand 「寸」 packing dirt 「土」 using a tool 「丵」
• Glyph origin of 「尊」 (ceremonial wine vessel used in rites), compound of simultaneously semantic and phonetic 「寸」 (picture of a hand) and semantic 「酋」 (picture of a wine vessel)
• Glyph evolution table of 「得」 (to obtain), originally semantic 「寸」 (hand) + semantic 「貝」 (money)
• Glyph evolution of 「持」 (to hold, grasp), originally semantic 「寸」 (hand) + phonetic 「𡳿」 (之)

Answer 2

There is no complete explanation on this question. But we could follow some explanations in history and fill the missing links ourselves.

1. The original character of 耐 is 耏.
2. The original meaning is not related to 寸, and not "endure" either.
3. 而 is a pictorial word about facial hairs.

說文, a dictionary written in 100 CE, has an entry about 耏, i.e. "耏，罪不至髡也。从而从彡。". A longer version is written in 說文解字注, "耏，罪不至髡也。从而从彡。耐，或从寸。諸法度字从寸。". This means 耐 is a variant form of 耏.

耏 is a penalty of removing one's hairs beside ears. It is lighter penalty than 髡, i.e. removing all hairs. The sentence "諸法度字从寸" indicates that later 耐 replaced 耏 for the meaning in laws. We might speculate that 寸 is a kind of measurement and further relates it to laws. 耐 finally wins the favourite form in the long history.

The meaning of "endure" is derivative. We could make a guess that one bearing this penalty must bear some kinds of humiliation. This might be the reason it derives the meanings of "bear, endure, resist and patient".