IPA: /ˈʌnjənˌskɪn/
KK: /ˈʌnjənˌskɪn/
A type of very thin and strong paper that is see-through and lightweight, often used for tracing or making copies.
The artist used onionskin paper to create delicate sketches that could be easily seen through.
Onionskin is formed from "onion" (from Old French *oignon*, meaning a bulbous vegetable) and "skin" (from Old English *scinn*, meaning the outer covering). The term "onionskin" refers to the thin, papery outer layer of an onion, resembling the texture of skin.
Think of the 'bulbous vegetable' ('onion') that has a 'thin outer covering' ('skin') — that's why onionskin refers to the delicate layer of an onion.