Perhaps from posh 'money, showy man' (19-20 centuries)
1a posh restaurant, hotel, car etc is expensive and looks as if it is used or owned by rich people:
a posh private school
2British Englishupper class:
Her parents are terribly posh.
WORD FOCUS: expensive WORD FOCUS: expensive highused about prices, rents, or charges fancyused about restaurants, cars, or clothes that look expensive poshused about hotels, restaurants, or cars that look expensive and are used by rich or high-class people cost a lotalsocost a bombinformalto be very expensive be out of somebody's price rangeto be more than someone can afford to pay be a rip-offinformalto be much too expensive, so that you feel you have been cheated exorbitantexorbitant prices are much too high ➔ See alsoexpensive
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.