Recorded in the Ming dynasty work 《
蠡海集·
历数》 by
王逵: the term originally came from astrology. The 60-year sexagenary cycle was divided into 'yang chen' (
阳辰) and 'yin chen' (
阴辰); when calculations slipped between the two, you had
阴错阳差 — yin-yang astronomical errors. The cosmic mismatch became a metaphor for everyday flukes.