clay (n.) Look up clay at Dictionary.com
Old English clæg "stiff, sticky earth; clay," from Proto-Germanic *klaijaz (cognates: Old High German kliwa "bran," German Kleie, Old Frisian klai "clay," Old Saxon klei, Middle Dutch clei, Danish klæg "clay;" also Old English clæman, Old Norse kleima, Old High German kleiman "to cover with clay"), from PIE root *glei- "clay" (cognates: Greek gloios "sticky matter;" Latin gluten "glue;" Old Church Slavonic glina "clay," glenu "slime, mucus;" Old Irish glenim "I cleave, adhere").

in Scripture, the stuff from which the body of the first man was formed; hence "human body" (especially when dead). Clay pigeon is from 1888. Feet of clay "fundamental weakness" is from Dan. ii:33.