"a call to drink to someone's health," 1690s (but said by Steele, 1709, to date to the reign of Charles II), originally referring to the beautiful or popular woman whose health is proposed and drunk to. The custom apparently has its origin in the use of spiced toast (n.1) to flavor drink; the lady being regarded as figuratively adding piquancy to the wine which was drunk to her health.
The custom itself is much older than this word for it, and the expectation of a bit of toast in a mug of ale at a tavern is well attested in many 17c. drinking songs, though none of them seems to give a reason for it.
Steele's story ["Tatler," No. 24] is that an (unnamed) beauty of the day was taking the cold waters at Bath, when a gentleman dipped his cup in the water and drank it to her health; another in his company wittily (or drunkenly) replied that, while he did not care for the drink, he would gladly enjoy the toast. Meaning "one whose health is proposed and drunk to" is from 1746. Toast-master attested from 1749.
"piece of bread browned by fire or dry heat," early 15c., from toast (v.1); originally as something added to wine, ale, etc. From 17c. in the modern sense as something eaten on its own with a spread. Slang meaning "a goner, person or thing already doomed or destroyed" is recorded by 1987, perhaps from notion of computer circuits being "fried," and with unconscious echoes of earlier figurative phrase to be had on toast (1886) "to be served up for eating." But other sources claim the extended sense and popularity is from the 1984 film "Ghostbusters."
"to propose or drink a toast," 1700, from toast (n.2). This probably is the source of the Jamaican and African-American vernacular word meaning "extemporaneous narrative poem or rap" (1962). Related: Toasted; toasting.
It forms all or part of: inter; Mediterranean; metatarsal; parterre; subterranean; tarsal; tarsus; Tartuffe; terra; terrace; terra-cotta; terrain; terran; terraqueous; terrarium; terrene; terrestrial; terrier; territory; thirst; toast; torrent; torrid; turmeric; tureen.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit tarsayati "dries up;" Avestan tarshu- "dry, solid;" Greek teresesthai "to become or be dry," tersainein "to make dry;" Latin torrere "dry up, parch," terra "earth, land;" Gothic þaursus "dry, barren," Old High German thurri, German dürr, Old English þyrre "dry;" Old English þurstig "thirsty."