Many words that existed in Old English did not survive into Modern English. There are also many words in Modern English that bear little or no resemblance in meaning to their Old English etymons. Some linguists estimate that as much as 80 percent of the lexicon of Old English was lost by the end of the Middle English period, including a large number of words formed by compounding, e.g. "bōchūs" ('bookhouse', 'library'), yet we still retain the component parts 'book' and 'house'