Source: Thomas Finkenstaedt; Dieter Wolff (1973). Ordered profusion; studies in dictionaries and the English lexicon.
About 85% of words in the English language are from three languages – Germanic, French and Latin. 12% are from Greek and other minor languages like Chinese and Japanese. About 4% are proper names.
Different languages had influence on English at different periods in history. Latin was the language of the Church. French came with the Norman conquest, etc.
Finally, these numbers are counting types (dictionary-like count of entries of words) and not actual usage of words (frequencies of individual words).