the word 'underskirt' is a transparent compound formed from two english elements of germanic origin. the prefix 'under', from old english, has consistently denoted a lower or concealed position since its proto-germanic root. the noun 'skirt' entered english from old norse, originally referring to a shirt or tunic, and later specializing to mean the lower part of a dress or a separate garment. when combined, the literal meaning "a skirt that is worn beneath" directly and logically describes the garment's function, evolving from its concrete components into a single term for a petticoat.

Structure: under (beneath) + skirt (garment) under: from old english under, meaning "beneath, below". functions as a prefix indicating position. skirt: from old norse skyrta, meaning "shirt, kirtle". functions as the core noun denoting a garment.