From Wiktionary, the free dictionary
đằng (“way; direction”) + ấy (“that”). Compare Japanese 彼方 (anata, “that way; you”).
đằng ấy
- (literal) that way, over there
đằng ấy
- (chiefly Northern Vietnam, familiar or humorous) you, my pal or gal
- Synonyms: ấy, cậu
- Antonyms: tớ, đằng này
Đằng ấy cứ đùa!- Don't be facetious, you!