The compound adjective 'three-yard' is a transparent and relatively modern English formation, combining the native numeral 'three' with the unit 'yard'. The word 'three' has a deep Indo-European heritage, traceable to the PIE root treyes-, which is the ancestor of the number three across many language families. 'Yard' has a more complex journey; its Old English meaning of "enclosure" evolved into a standard linear measure, originally conceptualized as the length from the tip of the nose to the thumb of an outstretched arm of a man. The logic of the compound is purely descriptive and mathematical, directly multiplying the unit by the numeral to specify a length. There is no metaphorical shift; the meaning remains the literal sum of its parts, representing a straightforward method of measurement specification in the English language.

Structure: three (numeral) + yard (unit of measurement) - three: From Old English 'þrīe', 'þrēo', from Proto-Germanic þrīz, from Proto-Indo-European tréyes. Functions as a numeral root. - yard: From Old English 'geard', meaning "enclosure, garden, court; a measure of length," from Proto-Germanic gardaz, from Proto-Indo-European gʰórdʰos, from the root gʰerdʰ- ("to enclose"). Functions as a noun root denoting a unit of linear measure.