Era name

The posthumous names of early Chinese rulers were often variations of a few words like "the martial one" 武 (wǔ), "the literary one" 文, "the filial one" 孝 (xiào), but by the Tang they had become so long that people began using rulers' temple names or era names instead.

Source: wiktionary

Cities were not infrequently named after the era name in which they were founded (e.g., Shaoxing 紹興 in Zhejiang, after the Shaoxing era, 1131-62).

Source: wiktionary