Originally an ideogrammic compound (會意): 石(“rock”) + 又(“hand”) — hand measuring a piece of rock. Also a phono-semantic compound (形聲), with 石 (OC *djaɡ) as a phonetic component. 石 is then corrupted into ⿸广廿.
Shuowen considers it to be a phono-semantic compound (形聲, OC *daːɡs, *daːɡ): phonetic 庶(OC *hljaɡs) + semantic 又.
From Proto-Sino-Tibetan*m-twa(“handspan”). Cognate with Tibetanམཐོ(mtho, “span; span of thumb and middle finger”), Burmeseထွာ(htwa, “to measure by a handspan; a quarter yard”), အထွာ(a.htwa, “handspan; quarter yard”), တွက်(twak, “to consider, to reckon; to calculate; to refuse to do things because others would not”), အတွက်(a.twak, “calculation; because of; for the sake of”). It is unclear whether Proto-Mon-Khmer*cɗaʔ(“span; handspan”) (whence Monဍ(daˀ, “to measure by spans of thumb and middle finger”)) is related. Related to 圖 (OC *daː, “to plan; to consider; plan; map”).
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