Sasisuseseso!🤍 #TWICE #DAHYUN

What happened

TWICE's Dahyun appears in a short clip whose only text is the title "사시스세소!" (sasiseseso), a string of five nonsense-looking syllables, alongside the group's own hashtags.

In the Korean comments

Several commenters use a nickname for Dahyun instead of her name: one writes that the video "너무 잘 어울리는" ("suits so well") her nickname "둡랑둥이," (doob-rang-doong-i, cute fan nickname for Dahyun) another calls her "둡냥이," (doob-nyang-i, Dahyun nickname with cat element) and a third just writes "둡 귀엽다" ("Doob is cute"). "둡" (doob) is a short pet-name fans use for Dahyun, and "냥이" (nyang-i, affectionate cat-related suffix) is an affectionate cat-related suffix — so these are fan nicknames stacked onto her name, not standard Korean words a dictionary would explain. The top comment adds a specific visual cue worth watching for: "뭐야 갑자기 앞머리 내려서 귀엽게 나타났네" (suddenly appeared with bangs down, looking cute) — in translation, "What, she suddenly showed up with her bangs down, looking cute — she was already cute, but now she's even more lovable," pointing to a hairstyle change (bangs down) as the reason this clip stood out to that viewer.

What the words mean

사시스세소 (sa-si-seu-se-so, playful vocal tongue-twister) literally is not a word — it's just the consonant ㅅ paired with five basic vowels in a row: 사 (sa, syllable in playful vocal sequence)(sa) 시 (si, syllable in playful vocal sequence)(si) 스(seu) 세 (se, syllable in playful vocal sequence)(se) 소 (so, syllable in playful vocal sequence)(so). Here it isn't being used to mean anything; it functions as a cute, sing-song string of sounds for Dahyun to say on camera, similar to a tongue-twister snippet. Register: playful and affectionate, not a phrase to look up.