The word “東西“ meaning ”things” came from “买東西“ which came from 买東又买西 which is preceded by 买了東又去西买 meaning after shopping from the east, go to the west to shop.
Just like modern shopping mall designs with two anchor tenants (JCPenney and Macy) at each end, ancient Chinese shopping malls 街 are similarly designed. One in the east and the other the west. In between are smaller shops offering goods and services complementing the two large market places of different trades. The markets are East (東/东dong) West (西xi) oriented.
Over the centuries people shopped from one end to the other. The term 买東买西/买東西 was thus coined and eventually 東西 came to mean “things” or goods. Real genuine goods, not made up.