means To grow or increase in size, quantity, or scope — or, as a noun, a graded system for measuring, a balance for weighing, or the protective plates on a fish or reptile.

from Several different words wearing the same coat. The 'climb' sense comes from Latin scala, 'ladder' (from scandere, 'to climb') — to scale a wall is to ladder up it. The 'weighing balance' sense comes from Old Norse skál, 'bowl' or 'drinking cup,' the dish that holds what's being weighed. And the fish-armor sense comes from Old French escale, 'husk' or 'shell,' related to words for splitting and flaking off — a cousin of 'shale' and 'shell.' Three meanings, three roots, one tidy English spelling.