I have now read in two different places on the Internet (which we all trust), that the name of Shaggy Soldier was inadvertently derived from its genus name. Galinsoga was named after Mariano Martinez Galinsoga, a Spanish Botanist. Someone with poor hearing thought it sounded like “Gallant Soldier” and also noticed that the stem was hairy (shaggy) and called it Shaggy Soldier, and the name stuck. This all sounds a little fishy to me, but I’ve seen no other explanation.
Another common name for this plant is Peruvian Daisy. It’s one of the few alien plants from South America that has established itself in North America.
Yet another common name is Quickweed. This is due to the fact that it reproduces so quickly. The seeds don’t need to go dormant so they can germinate the same season that they are created. I’ve never counted them myself, but one web page said that one plant can produce 7500 seeds.
By the way, if you google “quickweed seeds”, you’ll find a lot of pages selling marijuana seeds. Thought you might want to know that.