The Chinese custom of drinking tea has existed for a long time.
Tips
history
The phrase traces to the Liu-Song era collection 《世说新语·德行》, in the entry on 王子敬, which asks 由来有何异同得失 - what from the beginning had been right or wrong. It hardened into 由来已久 to mean 'has been so from the start.'
usage
Often used about customs, conflicts, or grievances. Neutral to slightly negative tone - frequently frames a problem as deeply rooted and therefore hard to fix.
