真 is old Daoist vocabulary: early forms suggest a transformed being ascending — the 真人, 'true person', the Daoist perfected immortal. Truth in Chinese began not as fact-checking but as spiritual authenticity.
真 intensifies half of spoken Chinese: 真好 (really good!), 真的吗? (really?! — the universal reaction), 真的假的?! ('true or fake?!' — modern disbelief). 认真 (earnest) and 真正 (genuine) carry its serious side. Daoists still call their adepts 真人; the internet calls surprising news 真的假的. Twenty centuries between them, one character asking the same question: is it real?
The perfected one, nothing false left — TRUE, REALLY.
真的假的?! ('real or fake?!') is the modern Chinese 'no way!' — skepticism compressed to four syllables.