There are many onomatopoeias in Japanese, and “doki doki (두근 두근) “is one of them.

“doki doki “means that the heart strikes hard.
If you exercise, your heart becomes”dokidoki “something good happens, when you are excited, when you expect something, when you worry, or when you ‘re upset, your heart rate gets faster, right?
The expression “doki doki suru (두근 두근)”is used to express such states

Some examples

사랑을하면 두근 두근한다.
Koi wo suru to doki-doki suru.
I feel excited when falling in love.

발견 버릴까 두근 두근했다.
Mitsukatte shimauka to doki-doki shita.
I was worried that the enemy would find me.

인터뷰의 순서를 두근 두근하면서 기다렸다.
Intabyuu no junban wo doki-doki shinagara matta.
I had butterflies in my stomach while waiting for my interview.

비행기를 타고 두근 두근한다.
Hikouki ni noru to doki-doki suru.
I get nervous when I board an airplane.

술을 마시면 두근 두근하기 때문에 마시지 않습니다.
Osake wo nomuto doki-doki surunode nomimasen.
I do not drink alcohol because my heart always beats if I drink.

오르면 두근 두근했다.
Kaidan wo noboruto doki-doki shita.
My heart beat so fast when I climbed up the stairs.

The origin of the Japanese word “doki-doki”?

There is a word “douki (어떻게 속 : 심장의 고동)”in Japanese.

This word is used like “douki ga suru (동계 (어떻게 속)이하는)”or “douki wo kanjiru ( 동계 (어떻게 속)을 감 (캔) 질) “when you feel palpitation.

For this reason, many Japanese believe that”doki doki “is derived from”douki “, but this does not seem to be the case. This is because “doki doki”and “douki”are used separately in the existing Edo period documents.

However, in the Showa era, some writers had a kind of play in their work , which they wrote “douki-douki (동계 동계)”and let the readers read it “doki doki”by giving “furigana”for the word.

(fURIGANA : furigana is comprised of small letters written or printed on the side of some kanjis to indicates how to read it. It may or may not be presented.
It is usually attached to the first kanji that appears, and the same reading does not appe ar afterward, because the reader is supposed to know it.
Children ‘s books may have a lot of furigana so that children can learn.)

It is thought that then people who read it started to mix up “doki-doki”and “douki-douki”

In any case “douki”means “doki-doki”, so I thought it was an interesting idea.