Middle English foode, fode, from Old English foda "food, nourishment; fuel," also figurative, from Proto-Germanic *fodon (source also of Swedish föda, Danish föde, Gothic fodeins), from Germanic *fod- "food," from PIE *pat-, extended form of root *pa- "to feed."
Food chain is by 1915. Food poisoning attested by 1864; food processor in the kitchen appliance sense from 1973; food stamp (n.) is from 1962.
early 14c., "quilted material worn under chain mail," from Old French estoffe "quilted material, furniture, provisions" (Modern French étoffe), from estoffer "to equip or stock," which according to French sources is from Old High German stopfon "to plug, stuff," or from a related Frankish word (see stop (v.)), but OED has "strong objections" to this.
Sense extended to material for working with in various trades (c. 1400), then "matter of an unspecified kind" (1570s). Meaning "narcotic, dope, drug" is attested from 1929. To know (one's) stuff "have a grasp on a subject" is recorded from 1927.