Unfortunately, our library catalog does not offer Irish (Gaeilge) as an option to search by language. Here are some other options for finding books in Irish or about Irish at the libraries:
Browse by call number
Search by Library of Congress Subject Headings
Search the catalog by subject heading to find book in or about Irish:
Fordham has a collection of over 600 volumes from the library of William Hubert McLees / Uilliam Hubert Mac Giolla Íosa and others. The majority of volumes are in Irish with a few in Scottish Gaelic and German published during the 19th and early 20th centuries.
Some of these titles are in located Special Collections and some are in the Stacks. Ask a Reference Librarian for tips about searching for this collection the catalog.