Named after the Oasis song of the same name which, despite being brilliant in many ways, has been rejected by many fans as "a bit wonderwall" due to over playing on air.
Person 2: "Only a million times already today... I did like it but now it's abit Wonderwall"
It is also a compound word.
Wonder- To be filled with admiration, amazement, or awe.
Wall- Any of various permanent upright constructions having a length much greater than the thickness and presenting a continuous surface except where pierced by doors, windows, etc.: used for shelter, protection, or privacy, or to subdivide interior space, to support floors, roofs, or the like, to retain earth, to fence in an area, etc.
So a wonderwall can be widely considered as a noun that is a strong foundation full of admiration.
In other words, it is something that gives you strength.
As it is a versatile expression, it may be used as an adj.
"I never realized before now, but that moment was my wonderwall."