the word "wingspan" is a transparent compound formed from two native english elements. "wing" originates from the old english wenge, a term for the limb used in flight, tracing back to proto-germanic. "span" comes from old english spann, originally referring to the distance measured by a spread hand, a concept of linear extent. when combined, these morphemes logically create a term that denotes the total linear distance between the extremities of two fully extended wings, a measurement first applied to birds and later extended to aircraft and other winged structures.

Structure: wing (wing) + span (distance) wing: from old english wenge (wing), of germanic origin; the body part of a bird, bat, or insect used for flying. span: from old english spann (distance between the tips of the thumb and little finger), of germanic origin; a full extent from end to end.