When words and phrases like "wack job," "mentally deranged" and "dotard" are exchanged, it's no surprise the U.S. and North Korea aren't allies.

President Trump and Kim Jong Un — despite coming together for a series of recent summits — have criticized each other over the years, with the North Korean dictator’s regime often jumping into the fray.

Here is a history of some of the insults between the two sides.

2013 – Trump calls Kim a ‘wack job’

In early 2013, North Korea became upset over a series of joint U.S.-South Korean military drills taking place on the side of the Korean Peninsula that’s more friendly to America.

The Hermit Kingdom’s state media then published a story on April 4 quoting a military spokesperson as saying that “we formally inform the White House and Pentagon that the ever-escalating U.S. hostile policy toward the DPRK and its reckless nuclear threat will be smashed by the strong will of all the united service personnel and people and cutting-edge smaller, lighter and diversified nuclear strike means of the DPRK.”

Two days later, Trump took to Twitter to warn then-President Obama to “be very careful” with the “28-year-old wack job in North Korea.”

“At some point we may have to get very tough,” he added.

2017 – Trump gives Kim a nickname: “Rocket Man”

After dubbing Kim “Rocket Man” in a September 2017 tweet, Trump rolled out the new nickname in front of world leaders during his inaugural address to the U.N. General Assembly.

"Rocket Man is on a suicide mission for himself and for his regime,” Trump had said in New York, pointedly warning Kim that the U.S. will “totally destroy” his country if he doesn’t abandon the pursuit of nuclear weapons.

In a follow-up tweet that week, Trump extended Kim’s nickname to “Little Rocket Man”.

2017 – Kim, after being called “Rocket Man,” says Trump is a “mentally deranged U.S. dotard” and “hard of hearing”

It didn’t take long for Kim to launch his own attacks at Trump after being called “Rocket Man.”

An official statement from Kim Jong Un in September 2017, in reference to Trump’s speech at the U.N., declared that “I will surely and definitely tame the mentally deranged U.S. dotard with fire.”

“Action is the best option in treating the dotard who, hard of hearing, is uttering only what he wants to say,” he added.

Merriam-Webster defines dotard as a “state or period of senile decay marked by decline of mental poise.” The word derives from the Middle English word “doten,” which means “to dote,” and initially meant “imbecile” when it was first used in the 14th century, the dictionary said.

2017 – Trump says Kim is a “sick puppy”

While giving a speech on tax reform in Missouri in November 2017, Trump digressed from the topic to call the North Korean leader a "sick puppy.”

“These massive tax cuts will be rocket fuel, hmm… Little Rocket Man, rocket fuel for the American economy,” Trump said, drawing cheers and laughter from the crowd. “He is a sick puppy.”

2019 – North Korean official describes Trump as a “heedless and erratic old man”

In December 2019, Trump tweeted that Kim, who has “far too much to lose… if he acts in a hostile way,” does “not want to void his special relationship with the President of the United States” or interfere in the upcoming 2020 presidential elections.

That led Kim Yong Chol, a senior North Korean official and former nuclear negotiator, to lash out at Trump.

“As (Trump) is such a heedless and erratic old man, the time when we cannot but call him a ‘dotard’ again may come,” the North Korean official was quoted by The Associated Press as saying. "Trump has too many things that he does not know about (North Korea). We have nothing more to lose."

A few days before that line of attack, a separate North Korean official — first vice foreign minister Choe Son Hui — warned Trump that the Hermit Kingdom might start calling him a “dotard” again if he didn’t let up on the “Rocket Man” nickname for Kim.

Kaitlyn Schallhorn, Nicole Darrah and Fox News' Alex Pappas contributed to this report.