大幅
おおはば · oohaba · JLPT N1 · na-adj
full width
大 — pictograph of a person with arms outstretched
大 is a pictograph showing a person standing with arms and legs spread wide. The outstretched arms suggest 'big' or 'great', extending from the literal image of a large stance to abstract meanings like important or grand. It is one of the oldest characters, found on oracle bones.
幅 — cloth radical 巾 + 畐 (full)
A semantic-phonetic compound: 巾 (cloth) gives the meaning, since 幅 originally referred to the width of a bolt of cloth. 畐 supplies the sound, related to 'fu'. The meaning later broadened to 'width' in general and to a measure word for paintings or scrolls.