The coinage of this word is usually attributed to Gyles Brandreth (see quotation below). The etymology is unexplained, but perhaps from or + -onym.
Meanings
A phrase or sentence that sounds the same as another phrase or sentence.
The comedian Jeff Foxworthy often uses oronyms in his Appalachian comedy routine, as when he uses a sentence with moustache: "I moustache [must ask] you a question." 2012, Rod L. Evans, chapter 14, in Tyrannosaurus Lex:
Vowel harmony may serve the purpose of parsing the morphosyntactic words in phrases (i.e., oronym avoidance). 2010, Andrew Nevins, Locality in Vowel Harmony, page 203:
[…]sometimes what you hear isn't what you're supposed to hear. Oronyms are sentences that can be read in two ways with the same sound. [1980, Gyles Brandreth, The Joy of Lex, New York, NY, United States: William Morrow and Company, Inc., page 58:
An oronym that comes from mishearing the lyrics of a song is most often called a mondegreen. 2008, Paul McFedries, The Complete Idiot's Guide to Weird Word Origins, page 101: