Image copyright Reuters Image caption Mr Trump turned 71 in June

On Friday the English-speaking world was startled to find itself suddenly reacquainted with the 14th-Century term "dotard", thanks to an unlikely source - Kim Jong-un.

The North Korean leader used the ancient word to describe Donald Trump several times in a fiery statement denouncing the US President's recent UN speech.

The statement was an unprecedented first person address to Mr Trump and as the diplomatic community digested its meaning, many others rushed to look up this unique insult.

Mr Kim used "dotard" not once, but twice, to refer to Mr Trump.

"Action is the best option in treating the dotard who, hard of hearing, is uttering only what he wants to say," Mr Kim wrote, displaying a keen sense of the original meaning of the word.

But he ended his screed with the ominous line: "I will surely and definitely tame the mentally deranged US dotard with fire."

So what exactly does "dotard" mean?

The Oxford English Dictionary defines it as "an old person, especially one who has become weak or senile".

Its US brethren, Merriam-Webster, further clarified that the word initially meant "imbecile", and stems from the Middle English word "doten" which means "to dote".

The word has made guest appearances in literature over the years but rarely with kind intent: it's there in Shakespeare, in works by Herman Melville about the menace of a shark and in an angry poetic stream of consciousness by Alfred, Lord Tennyson, for example.

This wasn't the first time North Korea used the term (we'll get to that in a minute), but it certainly was the first instance it garnered so much attention.

Unsurprisingly the word has spawned its own hashtag #dotard, which has since trended worldwide.

The Twitterverse sprang into action.

There were jokes laced with mild anxiety over the possibility of a nuclear holocaust.

Some have also matched it with Mr Trump's own term for Mr Kim.

Media playback is unsupported on your device Media caption Trump: 'Rocket Man's suicide mission'

But others did not find it funny.

Image copyright Reuters/KCNA Image caption Mr Kim is evidently not a fan of Mr Trump

Lost in translation?

But some observers are debating whether the Swiss-educated Mr Kim - or his English translator- really meant to use that word in the English statement.

They have pointed out that a slightly different term was used in the Korean-language version.

North Korea's rhetoric has its own special brand of bombast, and it particularly excels in epithets and ad hominem insults.

The US, for instance, is never just an enemy, but a "hooligan", "scoundrel", and a "gangster".

Never one to shy from misogyny and racism, North Korea has called former president Barack Obama a "wicked black monkey", while the dress sense of Mr Kim and Mr Trump's common enemy, Hillary Clinton, has been mocked as resembling both a "primary schoolgirl" and "a pensioner gone shopping".

But it perhaps reserved its most colourful insults for former South Korean President Park Geun-hye, known for her hardline stance against the North and popularly known as "the bitch" in Pyongyang.

Image copyright Reuters Image caption Ms Park was not best pleased about the labels

Revealing its penchant for animal-themed comparisons, North Korea has over the years called her "an ugly female bat-disgrace", "matchless dragon lady", "a tailless crazy old bitch", and an "old cat groaning in her sickbed".

It also appears to have form, as she has even been called - wait for it - a "dotard".