Ok I'll try to be more clear.
The original or first origin of matter itself or energy itself is unknown.
The origin of this particular formation of matter and energy (our observable universe) is theorized to have been the big bang.
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If something doesn't have an origin, it's hard for us to even imagine what that means.
But notice it's just as easily applied to reality. We can give the answer "energy and matter have always existed" (although IMO that's just as nonsensical as "God has always existed").

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If you just want to argue about what to call it (a popular past time here) sure, call it nature.
It's more than a name though. For example a supernatural god uses something like magic where things spontaneously pop into existence.
A natural higher power may, for example, create the earth by setting into motion the natural processes that eventually led to this planet. In that sense its function is more of a constructor and/or designer. The way you may imagine a person designing and then assembling a watch.
i don't have to imagine the watchmaker. We know and understand this process, albeit an incredibly complex process, it can be described and understood.