means Tasting of or full of sugar — or, by extension, so sweet in tone or sentiment that it verges on cloying.

from From "sugar" plus the adjective ending "-y." "Sugar" itself traveled a long road: from Sanskrit "sharkara" (originally meaning gravel or grit, fittingly, for sugar's crystalline grains) into Arabic "sukkar," then through medieval Latin and Old French into English. The "-y" ending, an old Germanic suffix meaning "having the quality of," makes the whole thing simply mean "sugar-like." The figurative sense — sweet to the point of insincerity — followed naturally, the way real sugar coats anything it touches.