Previous Post Wasn't he galen in a prior Universe, who merged with the Eternity of that Universe and came out as Galactus?

That is his origin, but it was not originally. Initially, if I remember the initial Thor story, he was Galen but he flew through a quasar or something for a much less noble reason.

The energy in that merged with him and he became what he is. Later, when Galactus gained status, and as the cosmic sphere grew the idea must have been to give him a place of honor, being such a critical piece of things. So they had him be the survivor of the previous universe merged with the dying sentience of that universe, or Eternity.

The original origin does not really flow with much have what has come after in any way, so it is largely just a footnote anyway.