>> English, like many other European languages such as German, has many loanwords from French, Latin, Greek, and probably even more.

That's what I hinted at with "it's a funny mix of other languages".

>> It makes sense Esperanto, an evolution on [in this case the commonly used world-languages English & Spanish] contains loanwords from those languages, perhaps even on top of French/Latin/Greek/...

Latin and Slavic with some Germanic in between. Zamenhof (Esperanto was his brainchild) came form Poland and spent his life on this idealistic project of his.

Also Spanish, French, part of German and by analog of the previous combined English are to a great part derived from Latin, so kinda the same roots here.