In Lamentations the word goy or ‘nations’ is used. There is no separate reference to ‘pagan’ which suggests that the translators wanted to differentiate it from Isaiah 56:6-7. The ‘nations’ entering the sanctuary was forbidden. During the days of Antiochus Epiphanes, the goyim, the Greeks, entered the sanctuary and defiled it with pig’s blood. Their actions were pagan and they were goyim.
Abraham did not become the ‘father of many pagans’ nor should every gentile be considered pagan. Abraham became the ‘father’ of many geographical peoples with many different origins, languages, and governmental identities: the goyim [nations]. Though those living in the nations may have had a pagan belief system, many within those systems recognize Abraham as their ‘father of faith.’ These are the goyim promised to ‘the father of many nations.’
The word nation in these verses is the Greek word ethnos from where the word ethnic comes from. Ethnic wars are also known as civil wars. Civil wars are not political wars between kingdoms like Canada and the United States or Iraq and Israel, but between the individual ethnic groups that make up the kingdoms.