Origin of the term "level up"
Solution 1:
Levelling up is based on the idea that you can achieve equality in two ways: either by making the rich worse off or the poor better off. Levelling down is where you take money away from the rich, levelling up is where you try and raise the status of the poor so everybody is on the same level (of income, opportunity, health, etc).
Politically it is a valuable idea because it indicates you're making some people better off, rather than making some people worse off. Politicians don't want to be seen to take money away from people.
According to the think-tank UK In A Changing Europe the first prominent use was in the 1860s in British debates over inequality in Ireland. They also quote a Labour MP in the 1940s as asking about different levels of benefits between London and the rest of Britain:
Cannot the anomaly be removed by levelling up the rates paid to the wives of serving men for the whole country to that paid in the London postal district?
In the 1990s Labour minister David Blunkett spoke of "levelling up, not levelling down".
It is unconnected to levelling up in video games, which has no sense of equality or getting everyone to the same level. In politics, part of the meaning is the sense of "level" meaning horizontal, although both the political and video game meanings also relate to "level" as the position on a scale: in politics you are getting everyone to the same position, reducing horizontal differences and achieving a flatter outcome.