Jan Freeman remarked on Twitter that she had been hearing the phrase “on the up and up” meaning “improving” instead of “honest.”
There are indeed two general meanings of the phrase. The one I’m familiar with is “honest” or “on the level,” and the OED identifies it as originally American, with citations going back to 1863.
The OED doesn’t specify any nationality for the “Steadily rising, improving, or increasing” meaning. The first citation is from The Baltimore Sun, 1930: “From now on, we are led to believe, law and order will be on the up and up, as the current phrase is.” But that strikes me as ambiguous–that is, it could mean that law and order is on the level, as opposed to on the rise. All the other citations are from British sources.
But in any case, as Jan suggests, it’s now being used in the U.S., as in this from a March post in Forbes.com: “to say that Thrive [Capital] is on the up and up would be a massive understatement.”
Any Yanks out there who have a sense that “on the up and up”=”on the rise” is a long-term thing over here?
notoneoffbritishisms.com 
I suspect it’s been misused for its literal connotation by the untutored ear so vastly that it’s been placed into legitimate circulation here as a term for “improving” when it should only rightly be used to describe something “on the level.”
I’ve never heard your “honest” meaning used in the UK.
Blimey – I read Thrive as being distinctly dishonest! And the police improving. A sneaky phrase this.
Sorry to clarify, in Thrive up and up IS meaning honest, but a is decried as such. And I’ve always heard up and up as honest. “He’s on the up and up” equals trustworthy.
Actually the forbes.com quote, in context, means Thrive Capital is prospering, not that they’re honest.
Thanks for checking this out, Ben! I did a cursory Google search (News? Books? don’t remember) when I noticed it, and the “improving” meaning there had a distinctly Brit bias, but that’s as far as I got.
In Canada,as far as I’ve ever heard it used, on the up and up means honest and on the up means increasing.
I must admit that I can only associate “up and up” with improvement, e.g “Sales are on the up and up!”
“Straight up” is used to denote honesty. It’s akin to saying “No, really!” or “No, honestly!” It was a cliche for Cockneys as in The Sweeney or Only Fools and Horses (“Straight up, guv!”)
“On the level” is the usual Transatlantic variant.
It’s funny – as an American (MidAtlantic) I associate “straight up” with hip-hop culture, mostly because of Paula Abdul’s song and that rap song “I’m a gangster, I’m a straight up g” which I can’t find a release year for. The second use is a little closer to “total/complete” than “honestly,” & I’ve heard it used in that sense since (“he’s a straight up boss”).
“On the up and up” = on the level/honest to my ears – but it also sounds like an older turn of phrase for me, & “on the level” feels more natural to say.
I–lifelong Californian, so far–first learned of the “improving” sense of “on the up and up” from a radio piece Geoff Nunberg did for “Fresh Air” in 2003: http://people.ischool.berkeley.edu/~nunberg/upandup.html
Nunberg: “The OED lists the sense ‘steadily rising, improving,’ but no American dictionary has cottoned to it.”
The subject may have been discussed in ADS-L, the American Dialect Society listserv, but I didn’t start subscribing until several years later.
This seems to be one of those instances where the transatlantic difference is clear-cut and unarguable. In the UK, “straight up” = honest(ly), “on the up (and up)” = improving. Full stop. Or rather period.
Yes – I don’t think you can say one is right and the other wrong – just that one is BritE and one is AmE.
I note the use of “on the level” as meaning “honest” but I believe its origins lay in Freemasonry, indicating membership. For Masons in the police this possibly has the opposite meaning of honesty.
“On the square” was an alternative, masonic/police, usage.