The music of O’Carolan
Dictionaries of the Celtic languages
Modern Irish: https://www.teanglann.ie/ga/
Scottish Gaelic: https://www.faclair.com
Manx: http://www.mannin.info/Mannin/fockleyr/e2m.php
Welsh: http://welsh-dictionary.ac.uk/gpc/gpc.html
Breton: https://en.glosbe.com/en/br
Cornish: https://www.cornishdictionary.org.uk/home?locale=en