Old English clæg "stiff, sticky earth; clay," from West Germanic *klaijaz (cf. 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" (cf. 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.
This word is used of sediment found in pits or in streets (Isa. 57:20; Jer. 38:60), of dust mixed with spittle (John 9:6), and of potter's clay (Isa. 41:25; Nah. 3:14; Jer. 18:1-6; Rom. 9:21). Clay was used for sealing (Job 38:14; Jer. 32:14). Our Lord's tomb may have been thus sealed (Matt. 27:66). The practice of sealing doors with clay is still common in the East. Clay was also in primitive times used for mortar (Gen. 11:3). The "clay ground" in which the large vessels of the temple were cast (1 Kings 7:46; 2 Chr. 4:17) was a compact loam fitted for the purpose. The expression literally rendered is, "in the thickness of the ground,", meaning, "in stiff ground" or in clay.