Blown to smithereens

Probably because the term has been associated to terms like blow or smash since its origin. Its usage can also be found outside military contexts as suggested in the extract from the MacMillan Dictionary below:

Blow to smithereens:

• The notion of things being 'broken/smashed/blown to smithereens' dates from at least the turn of the 19th century. Francis Plowden, in The History of Ireland, 1801, records a threat made against a Mr. Pounden by a group of Orangemen:

  • "If you don't be off directly, by the ghost of William, our deliverer, and by the orange we wear, we will break your carriage in smithereens, and hough your cattle and burn your house."

• 'Smithereens' is one of those unusual nouns that, like 'suds' and 'secateurs', never venture out by themselves - the word is always plural.

(The Phrase Finder)

Smithereens:

• Contrary to the bucolic imagery of Heaney’s verse, smithereens usually involve violence, or at least vigorous activity. Things get blown, bombed, blasted, bashed, dashed, smashed and shot to (or “into”) smithereens. This activity often implicates material items, such as bricks, cities, or the good crockery, but it can also occur in a more figurative sense: one’s hopes and dreams can be smashed to smithereens.

• The word’s popularity can probably be attributed at least partly to its euphony, the way it bounces out off the lips and teeth, pulling its Gaelic tail after it. But this is idle speculation. From its slightly obscure beginnings, in and out of Irish, smithereens has eased its way into all sorts of contexts, from descriptions of military destruction to poetic accounts of evolution. On that note, and to conclude, I leave you with a line by D. H. Lawrence:

  • Then someone mysteriously touched the button, and the sun went bang, with smithereens of birds bursting in all directions.

(MacMillan Dictionary)

Smithereens

• means tiny bits, shattered fragments. The word smithereens is often seen in the phrases blow, blew, blowing or blown to smithereens, and smash, smashes, smashing or smashed to smithereens.

• The word smithereens can be traced back to the Irish Gaelic word smidirin, which is a diminutive of the word smiodar, which means piece or fragment. The suffix -een was tacked on as an additional diminutive.

• Smithereens appears at the beginning of the nineteenth century, with the variant spellings smiddereens and shivereens appearing at about the same time. Today, only the spelling smithereens has survived.

(The Grammarist)

Stand on a chair, lift some crockery over your head and then drop it on an uncarpeted floor. Result: smithereens.

Example: "Inside the bathroom, the porcelain sink has been smashed to smithereens and the glass shower cubicle shattered."

How I found this example and many similar ones: I googled the following two words

smithereens porcelain

I have no idea where "Starts out as large flakes then it becomes smithereens once it goes through this machine" came from. It sounds strange to me too.

I wanted to point out an earlier instance of smithereens than the Phrase Finders' claimed 1801 occurrence in Francis Plowden, The History of Ireland, cited in user66974's answer.

From William Macready, The Bank Note, or, Lessons for Ladies: A Comedy in Five Acts (London, 1795):

Servant. A letter from Mrs. Flounce.

Sally. Let's see.—(exit Servant.)—Oh! what a seal!—a heart stuck with darts, like pins in a pincushion. (Reads) "Thou fairest of the fair.——I send you this by the Penny-Post,—and if the letter carrier does not give it to you directly, run to the Post-office to enquire for it, and then we'll be sure to meet, for i am going to your house immediately, where I hope you'll receive with exstacy, your ever agreeable and transported, William Killeavy." Pshaw!—what signifies transported, it would be something indeed if he had been hang'd,—or shot,—or——

Enter Killeavy.

Killeavy. I wish he was with all my heart.—If the rascal is troublesome to you,—who is he, my pet?

Sally. Who? Why, a person who pretends to love me.

Killeavy. Oh, then I join you with all my heart,—and wish he was hang'd, shot, cut in smithereens, or—

Sally. Ha! ha! ha! that’s a very good Joke,—why it was yourself I meant.

In the play, Killeavy is an Irish servant to a character named Sir Charles Leslie.

Jonathon Green, Chambers Slang Dictionary (2008) confirms that the form smithereens originated in Ireland:

smithereens n. (also flindereens) {SMITHERS n. + Irish dimin. -een, Share suggests Irish smiodar, a fragment} {mid-19C+} tiny fragments, atoms; esp. in phr. smashed to smithereens, blow/break/knock/split to/into smithereens, smashed to pieces, often in fig. use.

I had no luck finding eighteenth-century instances of smithers or flindereens, however.

Although "smashing to smithereens" sounds like an inherently violent process, Green is correct that the expression may be used figuratively to refer to such things as emotional tumults that involve no real-world violence. One such early example is from "The Can-Can," in The Book of Comic Songs and Recitations (1874):

A girl who lives up our Court, / Served me as she didn't ought; / And made of me a cruel sport, / Though after her I ran. /She knocked my heart to smithereens, / All for a chap of larger means, / Who made Java Coffee out of beans, / While she danced the Can-Can.

With regard to the Phrase Finder date of 1801 for smithereens in Francis Plowden, The History of Ireland, the quoted text actually appears in Plowden's The History of Ireland, From Its Union with Great Britain, in January 1801, to October 1810, volume 3 (1811), which reports that the word was used in a threatening anonymous note left near the hall door of a magistrate named Pounden in the summer of 1810:

The form of this notice was. "Mr. Pounden, Sir, we gave you notice some ago to quit this country ; for you are making a rebellion here. We tell you now again, that if you don't be off directly, by the ghost of William, our deliverer, and by the orange we wear, we will break your carriage in smithereens and hough your cattle, and burn your house—so mind yourself—you will soon hear again from your friend, TRUE BLUE"

It thus appears that the notice cited in The History of Ireland was written by night marauders in the summer of 1810 and reprinted in Plowden's history in 1811. The 1795 instance from Macready's play is 15 years older.