A tmesis is abso-freakin-lutely the coolest feature of the English language you don't know exists
You might be using it and don't even know it.

Believe or not, the tmesis has been around for thousands of years.
You might’ve never heard the word “tmesis,” but you’ve certainly heard one being used. Ever said something like “that’s a whole nother thing” or “no-friggin-way”? Congratulations, you’ve used a tmesis! As you can probably deduce, a tmesis is when a word is put smack dab in the middle of another word or phrase, usually to add emotional emphasis or comic effect. As speech writer Simon Lancaster put it, “Tmesis can make you sound inventive, anarchic, [and] amusing.”
The word itself comes from the ancient Greek word τμῆσις (tmêsis), meaning "a cutting.” In fact, Greek poet Homer used tmesis in The Odyssey. Throughout history, literary icons have been lovers of this rhetorical device. Take poet John Donne’s “In what-torn ship-so ever I embark," William Shakespeare’s “This is not Romeo, he is some-other-where.”
But the award for most impressive tmesis definitely goes to Mark Twain, who, for his essay “The Awful German Language,” wrote:
“The trunks being now ready, he DE-after kissing his mother and sisters, and once more pressing to his bosom his adored Gretchen, who, dressed in simple white muslin, with a single tuberose in the ample folds of her rich brown hair, had tottered feebly down the stairs, still pale from the terror and excitement of the past evening, but longing to lay her poor aching head yet once again upon the breast of him whom she loved more dearly than life itself-PARTED."
The tmesis is well-loved in today’s pop culture. Alan Gordon Partridge, a British parody character played by Steve Coogan, famously experimented with different ways to add "bloody" into the word "unbelievable," which became one of his most quotable moments among fans.
“Unbelievable. Un-bloody-believable. Unbe-bloody-lievable. Hang on, there’s one more. Unbelieva-bloody-ble.”
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Then there’s the animated character of Archer, who used the phrase "some-crazy-how.”
Or “Cinder-f**kin-rella” in Pretty Woman…
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And of course, we saved the most famous pop culture tmesis of all for last: “Legen-wait for it-dary.” Said many, many times by Neil Patrick Harris’ Barney from How I Met Your Mother.
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Many use a tmesis to add in an expletive (again for emotional emphasis, and because it’s just fun), as with fan-bloody-tastic, guaran-damn-teed, abso-freakin-lutely Jesus-tap-dancing-Christ, boo-f**kin-hoo, back-ass-wards, un-f**king-real, in-f**king-credible. But there are plenty of clean and safe ones too, like hot-diggity-dog, and scrum-diddly-umptious!
And while the tmesis might seem strictly an English-language device, the concept of word splitting and insertion appears in other languages, such as German, Dutch, Catalan, Finnish, French, and Mandarin Chinese, to some extent.
Still, you gotta admit that the chaotic slicing-and-dicing-and-inserting aspect feels very, very English, does it not? Yet one more colloquial quirk that makes it so hard to fully master, but easy to appreciate.