The OED reports that this diminutive for journalist originated in Australia in the 1960s, migrating to the UK no later than 1984, when this ominously prescient quote appeared in The Listener: “Rupert Murdoch once said, if the journos don’t like it they can always get out; there are plenty more journos on the street.”
The atmosphere was animated and perhaps a little self-satisfied—the New Hampshire primary is tremendous fun, and journos and politicos alike are always tickled to be part of it—but of boisterousness there was none. (Hendrik Hertzberg, The New Yorker, blog, January 8, 2008)/It’s been nearly a year since the release of UFOs: Generals, Pilots and Government Officials Go on the Record, journo Leslie Kean’s attempt to steer The Great Taboo into the arena of mainstream debate. (Sarasota Herald-Tribune, blog, July 29, 2011)
notoneoffbritishisms.com 
I’m a very liberal language person who spent 90 percent of his career (I recently retired) as a news reporter and editor(also magazines and books). I’m well aware of the English predilection for slanging words by adding an -o at the end; I had an English woman friend who said “goodo” all the time to indicate agreement. In this case it might be professional gravitas on my part, but I would be annoyed if someone were to introduce me to another person as a “journo-” sort of like introducing a reporter as a wordsmith, or a politician as a Solon, or a lawyer as an ambulance chaser. But if the word sticks in the US, I’ll just have to say, “goodo.”0
English tic
Living in England, being English and nearly 40 years old, I’ve never heard the word journo used. To be honest, we’d be more likely to say a newspaper reporter than a journalist anyway. I’d consider “journalist” to be an Americanism!! Not sure about the “English prediliction” for adding an “o” at the end of a word either. Isn’t that more of an Australian thing? I should think we’re more likely to add a “y”, as in “goody”, or “footy” (football); or an “er” as in “footer” (football) or rugger (rugby)
The only o suffixes I can think of that I have heard in use in the UK are goodo and righto, the first being an informal expression of approval and the second of agreement/compliance. Unless there are more than I’m not thinking of, I’m not sure two instances constitutes a predilection.
I’m English and although I use journo from time to time, I still consider it a self-concious “Aussie-ism”. Like many Brits in our 30s, I would date the invasion of Australian English into British English to the mid-1980s when the Australian daytime soaps ‘Neighbours’ and then ‘Home and Away’ took off in the UK. It’s Australian to take a the first syllable of any word and put an ‘o’ on the end to make a shortening.
So I’d look across the Pacific for this one, rather than across the Atlantic, although of course it could have snuck into NYC via London rather than coming direct from Sydney!
Interesting insights on the Australian connection. The footy and rugger examples by Kay suggest to me that the British have a predilection for all kinds of nicknames, pet names, etc., formed by adding an assortment of suffixes, as well as the letter “s”–as in “Wills”– and also by shortening words to the first syllable–as in veg and the likes of “Reg.” On the adding-an-o issue, I think of the veddy British nickname “Debo,” for Deborah Mitford.
Ben,
Wtf does ‘veddy’ mean? I’ve seen it for years in US writing and it makes no sense to me. I assumed that it was someone’s idea of ‘very’ spoken in some strange accent, although no English person I’ve ever met says anything like that. I certainly don’t and I am English.
Yes, I’ve seen that forever as a way of indicating English accents. I think it’s a way of suggesting that the English don’t come down harrrrd on the rrr, as Amerrricans do. As you say, they do not make a “d” sound–maybe closer to an “l”? I imagine a linguist would have some insight on this.
I’m not a linguist, just a Brit, so please excuse any inaccurate terminology – I’m not trying to show off but sometimes there is no appropriate non-specialist term, so it was either waffle on or have a stab at using them as best I can.
I start by noting that while on this side of the pond only speakers from Northern Ireland and the West Country of England pronounce final ‘r’s, Welsh, Scots and Irish speakers all have stronger non-final ‘r’s than RP English, as do Northern Irish and West Country speakers, and the Welsh and Scots also tend to roll them, as do Liverpudlians. Not just Britain but England retains a (diminishing) variety of accents; so it is not accurate to use ‘British’ or even ‘English’ (referring to the people of England) as a blanket term for pronunciation.
That said, “English” people only elide final ‘r’s, not all of them, although we do not ‘come down harrrrd’ on those we do pronounce. So when we “English” say ‘very’ we pronounce the ‘e’ rather than making it a schwa, following it with a fairly weak ‘r’ by comparison with a ‘harrrrd’ one. So: ‘vehry’ to rhyme with ‘ferry’ rather than ‘vurrry’ to rhyme with ‘furry’.
To my ears the American ‘r’ sometimes comes together with, and may well be the cause of, the articulation of a vowel as a schwa – as in ‘vurrrry’ – or the elision of a schwa – as in “hr”, “hrd” and “hrding” (her, heard and hurting) – and even the running together of two syllables into one, especially, maybe solely, in words with two ‘r’ syllables with an intervening BrEng schwa – as in “mirrrr”, “terrrr”, “terrrr’st”, “errrr”. However I don’t hear most of this happenng in Northern Irish English, which has a strong ‘r’ like (most) AmEng while managing to keep all the syllables.
‘Veddy’ is ludicrous; but, when spoken, may be as close to an English person’s ‘very’ as an AmEng speaker can get – somewhat like the tricks poor ventriloquists use with bilabial consonants (eg ‘gottle’ for ‘bottle’). Actually some prim and proper Brits will slightly roll the ‘r’, a little like the Parisian ‘hr’ sound in ‘Paris’, and ‘veddy’ is not so far off that. But I still think you ought to stop using it because it looks daft.
English East Midlands (and I lived in London for 16 years): I can’t remember hearing ‘journo’ spoken, except, perhaps, by an Australian.
Follow this Australian National University link https://slll.cass.anu.edu.au/centres/andc/meanings-origins/all and you’ll see ‘ambo’ = ambulance and ‘arvo’ = afternoon. ‘Journo’ isn’t listed, but the list is suspect; e.g. ‘bitser’ an abbreviation of ‘bits and pieces’? It’s short for ‘bitser this, bitser that’ surely?
Whether ‘goodo’ originated in Aus or the UK, it seems to be coming back into fashion here, if only because ‘goody’ has declined towards extinction. Incidentally, the also near-extinct ‘goody gumdrops’ may have originated in America: https://www.phrases.org.uk/meanings/goody-goody-gumdrops.html
Not all ‘o’ endings originated in the Anglosphere; we got ‘politico’ from Italian or Spanish.