pied d'éléphant
/ˌpjɛ ˌdɛlɪˈfɒ̃/ /ˌpjeɪ ˌdɛlɪˈfɒ̃/(also pied d'elephant) Mountaineering
noun
A padded sack used to protect the lower part of the body when sleeping outdoors in a bivouac.
Origin
1950s; earliest use found in Charles Evans (1918–1995), surgeon and mountaineer. From French pied d'éléphant from pied foot + de + éléphant.