Origin of arguable
Examples from the Web for arguably
Despite the actions of a flawed few, it is arguably the finest professional police force in the world.The Wildly Peaceful, Human, Almost Boring, Ultimately Great New York City Protests for Eric Garner|Mike Barnicle|December 8, 2014|DAILY BEAST
They need Florida, arguably, at least in Electoral College terms.
It was arguably the most important target the American drone program had ever taken out.Obama’s Deadly Informants: The Drone Spotters of Pakistan|Umar Farooq, Syed Fakhar Kakakhel|November 12, 2014|DAILY BEAST
Five, the tens or arguably hundreds of millions of dollars in dark money that flowed from corporate sources into GOP coffers.
On the other hand, service is arguably even more important in a bar than the drinks.
It seems that Mab was a stationer (arguably the publisher) and Harper the printer, not the author.