Muchly
Someone recently sent me an email that included the word "muchly", in the context of gratitude.
I suppose this is how the English language grows, by inventing new words and adopting existing ones from other languages. A word need only to catch on to be accepted as an word in the English language. Very democratic.
Other languages, notably French and Spanish, have official organizations to guard and track changes to the language. The Royal Academy of the Spanish Language, for example, keeps track of the geographic origin of a word (see http://www.rae.es/), as there are more Spanish speaker outside of Spain than there are in this European country.