From Shanghai dialect for mahjong partners (
牌搭子). Spread nationally on Xiaohongshu in 2023 as young urbanites, moving cities often and short on deep bonds, sought 'precision companionship' - one person per activity, no wider social obligation. Sociologists linked it to work mobility, atomization and friendship fatigue. Named a 2023 Top 10 buzzword by 《
咬文嚼字》.