This paper investigates the diachronic development of yuè lái yuè 越来越 (lit. ‘more come more’, meaning more and more) construction, a type of comparative correlatives in Chinese. It is argued that (i) the earliest usage of yue lai yue can be traced back to the late Qing dynasty (late 19th century), instead of the middle period as is widely accepted previously; (ii) contra Zhu (2010) and Long (2013) which syntactically decompose yue lai yue into yue…yue and the pro-verb lai, we propose an idiomatization analysis. More specifically, yue lai yue is derived from its spatial-oriented correlative homograph which appears in spatial-temporal ambiguous contexts; (iii) the evolution of yue lai yue is driven by its semantic change and the whole process involves four aspects of change, namely, desemanticization, decategorialization, context extension, and phonological erosion. Meanwhile, the prosody, namely Constraint on Sentential Intonation (CSI) in Chinese also plays an important role in shaping the coalescence of yue lai yue; (iv) yue lai yue can still be used separately as yue lai…yue… in certain contexts, even when the coalescence has completed. However, this kind of special usage is licensed by formal registers, evidenced by the fact that yue lai…yue… is only allowed in formal (literary) registers but not in informal ones. The study in the paper supports the argument that formal registers go upward to higher syntactic positions whereas informal registers go downward to lower syntactic positions. Furthermore, the characteristics of visual language (versus auditory language) is crucial to the development of yue lai yue as well.