- an abbreviated form of of, as in o'clock or will-o'-the-wisp.
- an abbreviated form of on.
Origin of o'
Middle English; by shortening.
- a prefix meaning “descendant,” in Irish family names: O'Brien; O'Connor.
Origin of O'
representing Irish ó descendant, Old Irish au
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- informal, or archaic shortened form of of a cup o' tea
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
as a prefix in Irish names, from Irish ó, ua (Old Irish au) "descendant."
Online Etymology Dictionary, © 2010 Douglas Harper