The term 'go after, as flies' can be solved by two four-letter words: SHAG and SWAT. The word SHAG is a verb meaning to pursue or chase after someone or something. It is derived from the Old Norse word skaga, which means to hunt or pursue. The word SWAT is also a verb meaning to hit or strike with a quick, forceful motion. It is derived from the Old English word swættan, which means to beat or strike. Both words are commonly used in reference to chasing after or hitting a flying insect such as a fly.