"Tongs" are a device for grabbing something. You often see them used as serving utensils for tossed salad and other foods:
Since a tong by itself would not be that useful, they come in pairs, which is why the plural "tongs" is typically used.
In the USA and Canada, a "tong" is also a gathering place of Chinese immigrants who belong to a secret society or some group with illegal activities. The vast majority of Americans are unaware of this meaning.
There is also the very similar word "thong", which was generally thought of as meaning a special kind of sandal:
As you would expect, thongs come in pairs, so the plural is typically used.
Also, many of the older generation lament that the word "thong" has become more commonly understood to mean very scanty underwear worn by women, and worse, by men. Sorry, no hyperlink for that one!
I do not recall hearing "donk" in the USA. However, the word reportedly has several meanings in the UK and Australia:
Also, the word appears to mean someone who plays poker very poorly, and it can be used as a verb, as in hitting someone. However, if you use "donk" in the USA, most people will have no idea what you're saying.