"I lie" is "뻥치다"(ppŏng-chi-da) in Korean.
The 뻥치다 (Bbeongchida), lie, exaggerated to say that.
뻥 (bbeong, lie) + 치다 (Chida, hit).
뻥 (bbeong), although it was originally meaning of "exaggerated say", but now it is often used in the sense of a lie to young people.
거짓말 (Geojitmal, lie) in the slang of, words to say well to friends and under the eyes.