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).
2.
a suffix occurring in colloquial noun or adjective derivatives, usually grammatically isolated, as in address:
cheerio; kiddo; neato; righto.
Origin
perhaps orig. the interjection O, appended to words as in def 2; as a derivational suffix reinforced by clipped forms of words with -o- as a linking element (e.g., photo, stereo), by Rom nouns ending in o, and by personal nouns such as bimbo and bozo, of obscure origin
British Dictionary definitions for -o
-o
suffix
1.
forming informal and slang variants and abbreviations, esp of nouns: wino, lie doggo, Jacko
Word Origin
probably special use of oh
Slang definitions & phrases for -o
-o
suffix
used to form adjectives
Having the indicated characteristics: berserko/ luxo/ neato/ sicko/ wrongo
used to form nouns 2: foldo/ freako/ klutzo/ muso •This fanciful formation is increasingly current