The compound adjective "three-foot-tall" is a modern English construct built from three distinct native elements. "Three" is an ancient numeral from Proto-Indo-European tréyes, which evolved through Proto-Germanic into Old English. "Foot" originates from the Proto-Germanic noun fōts, referring to the body part, which was later standardized as a unit of length. "Tall" has a more obscure history, entering Middle English with meanings related to comeliness before specializing in describing vertical stature. The logic of the compound is transparently descriptive, sequentially combining a numerical quantity, a standard unit of measurement, and the dimension of height to create a precise adjectival phrase for measurement.

Structure: three (number) + foot (unit) + tall (height) - three: From Old English þrīe, þrēo, of Proto-Germanic origin; related to Dutch drie and German drei. Functions as a cardinal number. - foot: From Old English fōt, of Germanic origin; related to Dutch voet and German Fuß. Functions as a noun denoting a unit of linear measure. - tall: From Middle English tal, tall, meaning 'seemly, handsome'; of uncertain origin, possibly from Old English getæl 'swift, ready'. Functions as an adjective describing great height.