Based on the OED, the Historical Thesaurus of the OED (HTOED) contains almost every word in English from Old English to the present, allowing users to explore words connected in meaning throughout the history of the language. It is a semantic index to the contents of the OED, is searchable and also has a browsable taxonomic classification. The Historical Thesaurus is a unique resource for scholars researching linguistic and literary history, the history of the language, social history, and more, and is a complement to the OED itself, allowing the words in the OED to be cross-referenced and viewed in wholly new ways. For more information see: this page.
Old English through current English language