埋める is “to bury.” 合わせる is “to unify together.” If you bury somebody in order to unify them with you, you’re almost certainly trying to compensate for something.
I’m having a bit of a problem internalizing where this word came from and how it makes any sense as a combination of these concepts. I’m sure that like many other abstract concepts, this one is also rooted in some physical process, but unfortunately the Crabinator’s breakdown of this word has left me devoid of any comprehensible associations.
If anyone can help me make more sense of this word, I would greatly appreciate it!
As mentioned in that other thread, 埋める itself can mean “to compensate for,” in the sense of addressing a shortage or a deficit and evening things out. The literal meaning of 埋める is “to bury,” but how do you bury something? You fill a hole in the ground. So it’s this act of taking a hole and filling it that lends 埋める its abstract meaning.
One of the glosses of 合わせる is “to match.”
So 埋め合わせる is just a combination of those verbs, emphasizing the resulting evenness, and it’s like “to even things out and match them up.” If they weren’t even before, you’re making up for a previous deficit. You are compensating for that previous deficit.