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》.