As in, "My sister-in-law, Debbie, is a wonderful person."
-ful - Old English, meaning full.
wonder - Also Old English meaning the object of astonishment. The word can be traced back further to proto-Germanic word wundran.
The original Old English word that means exactly the same as today was wunderfull. This is a word that dates back, unchanged, to the pre-dawn of the English Language.