toastyoudaoicibaDictYouDict[toast 词源字典]
toast: [14] Toast comes via Old French toster ‘roast, grill’ from Vulgar Latin *tostāre, a derivative of the past participle of Latin torrēre ‘parch’ (source of English torrid). Its use as a noun, meaning ‘toasted bread’, dates from the 15th century. It was common to put sippets or croutons of spiced toast into drinks to improve their flavour, and it was the custom of gallants in the 17th century, when (as they frequently did) they drank the health of ladies, to say that the name of the lady in question enhanced the flavour of their drink better than any toast.

That is supposedly the origin of the use of the term toast for ‘drinking someone’s health’.

=> thirst, torrent, torrid[toast etymology, toast origin, 英语词源]
toast (v.1)youdaoicibaDictYouDict
"to brown with heat," late 14c., from Old French toster "to toast, to grill, roast, burn" (12c.), from Vulgar Latin *tostare (source of Italian tostare, Spanish tostar), frequentative of Latin torrere (past participle tostus) "to parch" (see terrain). Related: Toasted; toasting.
toast (v.2)youdaoicibaDictYouDict
"to propose or drink a toast," 1700, from toast (n.1). This probably is the source of the Jamaican and U.S. black word meaning "extemporaneous narrative poem or rap" (1962). Related: Toasted; toasting.
toast (n.1)youdaoicibaDictYouDict
"a call to drink to someone's health," 1700 (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. The custom apparently has its origin in the use of spiced toast (n.2) to flavor drink, the lady being regarded as figuratively adding piquancy to the wine in which her health was drunk. 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.
toast (n.2)youdaoicibaDictYouDict
"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."