What is a ‘thing’? A ‘thing’, it seems, can be anything.
In Chinese, however, it’s ‘east’ and ‘west’. Honest, that’s how we say ‘thing’: 東西 （pronounced dongxi in Mandarin). 東 (dong) means east and 西 (xi) means west. Put them together and they mean ‘thing’.
The thing is, we have fifty thousand characters already so we have to reuse some of them to make new words, rather than create even more characters. So do we dip our hands into a bag of characters like Scrabble and make them up as we go? No, no, no. Well, maybe yes – I don’t know. Some origins of words are well documented : like the word ‘contradiction’ 矛盾 （mao dun）is made up of 矛 (mao) ‘spear’ and (dun) 盾 ‘shield’. But that’s another story. There is nothing that explains the ‘thing’ as neatly as The Spear and Shield Story that explains ‘contradiction’.
There are only theories. One goes: the ancients used to shop at the East and West markets in the city of Chang An, so to ‘go shopping’ is said to ‘買東西‘ （mai dong xi）’buy East West’ (i.e. buying ‘things’ at the markets – we Chinese would do anything not to say things in too many words, especially as you had to write it with a brush.
Another theory goes: the Chinese believes that all things belong to one of the five elements, and the only two elements that are matters that you can chuck in a bag is metal and wood and their position is East and West. So all objects and matters are 東西. I rather like that. Makes sense: you can’t chuck fire and water into a bag. Haha
In case you want to hear the Spear and Shield Story:
Once upon a time, a man tried to sell his spears and shields at the market by claiming that his spears can penetrate any shield and his shields can block any spears – get it?