scale

English has three separate words scale. The oldest, ‘pan of a balance’ [13], was borrowed from Old Norse skál ‘bowl, drinking cup’ (ancestor of Swedish skåal, from which English gets the toast skol [16]). This was descended from a Germanic base *skal-, *skel-, *skul-, denoting ‘split, divide, peel’, which also produced English scalp, shell, shelter, shield, skill, probably skull, and also scale ‘external plate on fish, etc’ [14]. This second scale was borrowed from Old French escale, which itself was acquired from prehistoric Germanic *skalō – another derivative of *skal-. Its modern German descendant, schale, is the probable source of English shale [18]. The third scale, which originally meant ‘ladder’ [15], came from Latin scāla ‘ladder’, a descendant of the same base as Latin scandere ‘climb’, from which English gets ascend, descend, scan, and scandal. (In modern French scāla has evolved to échelle, whose derivative échelon has given English echelon [18].) The modern meanings of the word, variations on the theme ‘system of graduations used for measuring’, are metaphorical extensions of the original ‘ladder, steps’. Its use as a verb, meaning ‘climb’, goes back to the medieval Latin derivative scālāre. => SCALP, SHELL, SHELTER, SHIELD, SKILL, SKOL, SKULL; SHALE; ASCEND, DESCEND, ECHELON, SCAN, SCANDAL

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   In the senses 'horny body covering' and 'weighing instrument,' the word is Germanic in origin, from a source that also gave shell. In the senses 'set of graded points' and 'to climb,' the origin is in Latin scala, 'ladder.'