a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; condo; limo; promo); -o also forms nouns, usually derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (cheapo; pinko; sicko; weirdo; wino).
a suffix occurring in colloquial noun or adjective derivatives, usually grammatically isolated, as in address: cheerio; kiddo; neato; righto.
Origin of -o
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
forming informal and slang variants and abbreviations, esp of nounswino; lie doggo; Jacko
Word Origin for -o
probably special use of oh
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