After enough back-and-forth, he even picked up some Chinese.
Tips
history
Attested in 《红楼梦》 ch. 58: 一来二去,两个人就装糊涂了 - 'over repeated exchanges the two of them played dumb'. Qing novels fixed this colloquial rhythm as a canonical idiom.
usage
Almost always sentence-initial, describing a gradual outcome that emerges from repeated small interactions. Pairs well with verbs like 熟了, 成了, 学会了.