"inter-library loan" vs. "interlibrary loan" Google Books Ngram Viewer data comparing across the full corpus (1870–2019), and it gives a real number: around 1925. Here's what the data shows: 1870s–1910s: The hyphenated form dominates entirely — this matches Green's 1876 "Inter-Library Loan of Books" and the early ALA-era usage we found in Library Journal. ~1900s–1920: Both forms are climbing in frequency (unsurprising, as ILL practice was growing), with hyphenated still clearly ahead. 1/2