Sentimental
adjective : having an excess of sentiment or sensibility : having or expressing strong feelings of love, sadness, etc., in a way that may seem foolish or excessive
Next morning Fred showed me one of the crumpled flowers in his vest pocket, and looked very sentimental.
— Louisa May Alcott, Little Women, 1868-9
Being sentimental was originally a good thing. Sentimental meant "marked or governed by feeling, sensibility, or emotional idealism." If you were sentimental you had a kind of emotional intelligence, in modern terms. The word comes, of course, from sentiment, which has the same origin—Latin sentire, meaning "to feel,"—as consent and sensible.
Chocolate-box
adjective : superficially pretty or sentimental
Gloriously decorative and perhaps somewhat too easy on the eye, their work cannot quite be dismissed as chocolate-box art.
— Robin Duthy, Connoisseur, June 1990
While the chocolate boxes of today may tend toward uniformly but elegantly shiny wrappings, time was chocolate boxes were adorned with lovely and charming pictures. Which apparently didn't charm all who encountered them. By the late 1800s, chocolate-box was being applied as an adjective to things superficially pretty or sentimental.
Moonstruck
adjective : affected by or as if by the moon: such as a : mentally unbalanced b : romantically sentimental c : lost in fantasy or reverie
On the floor are many copies, looking as if fluttered down from a balloon. The way they came there was this: A somewhat elderly person … had, without speaking, handed about the odes, which, for the most part, after a cursory glance, had been disrespectfully tossed aside, as no doubt, the moonstruck production of some wandering rhapsodist.
Herman Melville, The Confidence-Man, 1857
The poor moon: it's always being blamed for human foibles and failings. John Milton clearly struck a chord when he wrote of "moonstruck madness" in Paradise Lost (1674). The power credited to the moon in the word carries the assertion that people can be struck by the moon's beams—which over the centuries has been believed to unsettle and disrupt the minds and hearts of many in various ways.
Spoony
adjective 1 : silly, foolish; especially : unduly sentimental 2 : being sentimentally in love
She inclines her body toward his. They look spoony. After all these years. He plays with her hair.
— Richard Bausch, Esquire, August 1990
The word spoony might accurately describe the couple staring deep into one another's eyes all the time, but that pair might not like the history of the word. In 19th century British English slang, the word spoon was a noun that referred to someone who lacked common sense, perhaps because that person's intellectual depth was perceived to be as shallow as some spoons. The noun use led eventually to the adjective use with the meaning "silly" or "foolish." The "unduly sentimental" and "being sentimentally in love" meanings followed shortly thereafter.
The Castle Hill development company, chartered in 1887, built the six-acre Lake Loraine Park near what’s now Manderson Landing. The damned creek was surrounded by a skating rink, dance floor, croquet court and a rustic bridge the newspaper said was designed to “furnish quiet retreats for spoony couples.”
— Tuscaloosa News, 31 Dec. 2019
Corny
adjective : mawkishly old-fashioned : tiresomely simple and sentimental
The customers seemed to like corny music in there. Perhaps they were all tired out trying to be ahead of the minute in the place where they worked.
— Raymond Chandler, High Window, 1942
When Chaucer used the word corny in the 14th century he was describing ale that tasted strongly of malt—that is, grain (especially barley) that's soaked in water and used in making beer and whiskey and the like. As far as we can tell, it wasn't until a couple centuries later that the word was used with a more logical meaning: "of or relating to corn."
By the early 20th century, people seemed to have mostly forgotten the usefulness of the word corny to describe malty beers. The association of the word with all things corn apparently extended to things associated with life where corn is grown, out in the country. And it must have been some citified folk who decided to apply the word newly to things that reminded them of corn country: the word came to describe overly simple and sentimental things.
Cloying
adjective : disgusting or distasteful by reason of excess; also : excessively sweet or sentimental
The fable is sweet without being cloying, light without being too airy, suspenseful and sexy without being so much so that a parent has to distract himself with a lot of guidance.
— Richard Schickel, Time, 19 Dec. 1988This staging is very physical, and also quite bloody by the end, and he commits to all of it. Jenna Rubaii as Mary Magdalene is sweet without being dipsy or cloying in the slightest, and can sing the famous ballad ("I Don't Know How to Love Him") with original touches that render it hers.
— Karen Bovard, Broadway World, 26 Jan. 2020
Cloying is one of those adjectives that looks like a verb—and it does, in fact, come from one. Just how do you go about cloying?, one might wonder. Well, if you cloy you give or supply someone with an excess of something that was originally pleasing. Before the word had that meaning it had two others: "to clog," and "to prick a horse with a nail in shoeing." It traces back to the Latin word clavus, which means "nail."
Crush
noun : an intense and usually passing infatuation; also : the object of infatuation
I had a crush this spring. The object of my affections was a kind, intelligent, good-looking man….
— Lucy Ferriss, The New York Times Magazine, 22 Sept. 1991
While the infatuation crush doesn't typically call violence to mind, it is etymologically related to the verb most commonly understood to mean "to squeeze or force by pressure so as to alter or destroy structure," as in "crushing grapes." Though centuries newer, anyone who's ever had a crush knows that the feeling of having a crush can be not unsimilar to the feeling of being squeezed or forced by pressure.