"kakaotalk" is "카카오톡"(ka-ka-o-tok) in Korean.
That of Korean smartphone messenger application (app). The short term for this is 카톡 (Ka talk). In addition, KakaoTalk has variet "Kakao Story application name (카카오 스토리)" of social networking services (SNS). KakaoTalk and also LINE in Korea is commonly used in South Korea.