This passage continues the metaphor of Yahweh's extreme anger as wine that he causes the people of the nations to drink from a cup. (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "nations" represents the people of the nations. AT: "I made all the people of the nations ... drink the wine from the cup" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The word "hissing" refers to a sound that shows strong disapproval. Both "hissing" and "cursing" can be translated with a verbal phrase. AT: "an object at which people hiss and which they curse"
Possible meanings are that this phrase 1) refers to the time when the book of Jeremiah was written and some time after Jeremiah had proclaimed this prophecy or 2) means that the things about which Jeremiah prophesies here have already started to happen.