Naver's Korean dictionary defines 아량전 (亞兩箭) as follows:
"호죽(楛竹)ㆍ쇠심줄ㆍ새의 깃ㆍ복숭아 껍질ㆍ아교(阿膠) 따위의 일곱 가지 재료(材料)로 만든 화살. 무게가 약 150g"
箭 (전) means "arrow," so 아량전 was a kind of arrow. It was supposedly made from seven materials, including bird feathers (새의 깃), ox-hide glue (아교), ox tendons (쇠심줄), and the skin of a peach (복숭아 껍질).
To make an arrow, using bird feathers for the fletching makes sense, ox-hide glue to glue the feathers onto the shaft makes sense, and ox tendons to tie the arrowhead to the shaft makes sense, but what was the purpose of the peach skin?