sustentaculum
/ˌsʌstɛnˈtakjʊləm/noun
A supporting part or structure; especially the sustentaculum tali; Zoology a short spine present on each tarsus of the fourth pair of legs in many orb-weaving spiders (family Araneidae).
Origin
Mid 18th century; earliest use found in The Gentleman's Magazine. From post-classical Latin sustentaculum nourishment, food, crutch, prop from classical Latin sustentāre + -culum.