on request - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
When asked for, as in The agreement states that the rights on this book revert to the author on request. [c. 1800] Also see by request.