Understanding in Chinese happens in the heart, not the head: the heart radical 忄 marks 懂 as an inner event. 董 — itself a surname and 'to manage' — donates the sound. To 懂 is to have something settle into the heart and stay.
懂了 'got it' is the shortest complete conversation in Chinese classrooms. Its opposite, 听不懂 'hear-not-understand', is the honest flag every learner waves daily — and 懂王 'Mr. Know-It-All' is the internet's favorite sarcastic crown.
When the heart 忄 finally supervises 董 the chaos — you UNDERSTAND.
你懂的 'you know what I mean' became a national meme — the phrase for everything that everyone understands and no one says.