ornamental hairpiece
鈿 centers on a decorative hair ornament, specifically an ornamental hairpiece. It refers to a metal or jeweled accessory worn in the hair.
鈿 combines 金 (metal) with 田, which likely acts as a phonetic component. The character originally referred to a metal hair ornament, often inlaid with precious materials.
The left side 金 (metal) and right side 田 (field) together suggest a metal piece shaped like a field pattern, worn as a decorative hairpiece.
For デン, imagine a den of elegant ladies, each wearing a shiny metal hairpiece: den -> デン.