“Simkung” (심쿵) — heart, thud
The Sino-Korean word for heart bolted to the native sound of something heavy landing. One hit, always positive, and completely untranslatable in four characters.
seolleda
“Seolleda” (설레다) — the flutter that only happens beforehand
It points forward, always. Once the thing is happening the word stops applying — which is why “I don’t feel it any more” is a complete reason to end a relationship in Korean.