sweet

First recorded before 900; (adjective and adverb) Middle English swet(e), Old English swēte (adjective); (noun) Middle English swet(e), derivative of the adjective; cognate with Old Saxon swōti, Old High German swuozi (German süss ); akin to Dutch zoet, Old Norse sætr, Gothic suts, Sanskrit svādú-, Greek hēdýs, hādýs “sweet,” Latin suāvis “pleasant” and suādēre “to recommend”

It is not very often that a modern English word comes as close to its Proto-Indo-European original as, say, Latin or Greek does, but sweet is one of them.
The Proto-Indo-European root is swād- “sweet”; the adjective from that root is swādús, which becomes Sanskrit svādús, then Greek hēdýs and hādýs (with the usual simplification of initial sw- to h- ). The extended form swādwis becomes the Latin adjective suāvis “agreeable to the taste” (not necessarily sweet), “fragrant; pleasing to the eyes, the feelings, the mind,” and the verb suādēre “to recommend, make something pleasant.” The root swād- regularly becomes swōt- in Germanic, and the adjective from that root is swōtjaz. The j causes umlaut of the ō, becoming œ or ē and yielding the Old English adjective swœte and swēte, Middle English swet(e), swet, and English sweet.
Very early on, sweet was applied more generally to things that are pleasing or agreeable to bodily senses other than taste buds. In the 14th century, you might say someone was sweet in (the) bed to mean that they were good in bed. From the mid-1500s, sweet-love (now obsolete) was a term of affection for a beloved person. By the late 1500s, you could call someone sweet-tongued, and by the 1900s, whisper sweet nothings to someone.