sweetyoudaoicibaDictYouDict[sweet 词源字典]
sweet: [OE] Sweet is part of an ancient family of ‘sweet’-words that goes back to the Indo- European base *swād-. From this evolved Greek hēdús ‘sweet’ (and also hēdoné ‘pleasure’, source of English hedonism [19]), Latin suāvis ‘sweet, pleasant’ (source of English suave) and suādēre ‘advise’ (source of English dissuade and persuade), and Sanskrit svādús ‘pleasanttasting’.

Its Germanic descendant was *swōtja-, which evolved into German süss, Dutch zoot, Swedish söt, Danish sød, and English sweet. The use of the noun sweet for a ‘piece of confectionery’ (presumably short for sweetmeat [15]) dates from the mid-19th century.

=> dissuade, hedonism, persuade, suave[sweet etymology, sweet origin, 英语词源]
sweet (adj.)youdaoicibaDictYouDict
Old English swete "pleasing to the senses, mind or feelings; having a pleasant disposition," from Proto-Germanic *swotja- (cognates: Old Saxon swoti, Old Frisian swet, Swedish söt, Danish sød, Middle Dutch soete, Dutch zoet, Old High German swuozi, German süß), from PIE root *swad- "sweet, pleasant" (Sanskrit svadus "sweet;" Greek hedys "sweet, pleasant, agreeable," hedone "pleasure;" Latin suavis "pleasant" (not especially of taste), suadere "to advise," properly "to make something pleasant to"). Words for "sweet" in Indo-European languages typically are used for other sense as well and in general for "pleasing."
Then come kiss me, sweet-and-twenty!
Youth's a stuff will not endure.
["Twelfth Night"]
Also "being in a sound or wholesome state" (mid-13c.), and, of water, "fresh, not salt" (late Old English). As an intensifier from 1958. Sweet in bed (c. 1300) was the equivalent of modern "good in bed." To be sweet on someone is first recorded 1690s. Sweet sixteen first recorded 1767. Sweet dreams as a parting to one going to sleep is attested from 1897, short for sweet dreams to you, etc. Sweet-and-sour in cookery is from 1723 and not originally of oriental food. Sweet nothings "sentimental trivialities" is from 1900. Sweet spot is from 1976, first in reference to tennis rackets. Sweet corn is from 1640s.
sweet (n.)youdaoicibaDictYouDict
c. 1300, "something sweet to the taste," also "beloved one," from sweet (adj.); the specific meaning "candy drop" is 1851 (earlier sweetie, 1721). Meaning "one who is dear to another" is from 14c. Old English swete (n.) meant "sweetness."