由来已久

yóu lái yǐ jiǔ

long-standing

Character by character

由yóu
origin

来lái
come

已yǐ
already

久jiǔ
long

这两家公司的矛盾由来已久。

The feud between the two companies goes back a long way.

Tone: neutral.

For problems, customs or disputes with long histories.

Learn it in context

This idiom and thousands more are in Learn Chinese with Bao, with audio, pinyin and drills that make them stick.