As I understand, 梁启超 (Liáng Qǐchāo) is a famous Chinese patriot, who opposed imperialism and European influence prior to and during World War I. My teacher mentioned a quote from him (少年强则中国强), so I looked it up and found this:
Each part of this quote has a similar structure, e.g., 少年强则国强, which means something along the lines of "strong youth leads to strong country".
However, I don't understand 雄于 in this quote. I've only ever encountered 雄 previously in 英雄 ("hero"). I didn't find anything meaningful on YouDao or Jukuu, so I'd guess 雄于 is particular to this quote.
Question: What does 雄于 in 少年雄于地球，则国雄于地球 mean?