To complicate something is to make it more difficult or confusing by adding extra parts or details. It often turns a simple situation into a harder one.
From Latin 'complicāre' meaning 'to fold together, entangle'. Over time the idea of 'folding together' turned into the modern sense of making something tangled and hard to deal with.
The root idea is like folding a paper many times—each fold hides parts and makes it harder to see the whole sheet. When we complicate things, we mentally 'fold' them so much that the original simple idea disappears from view.
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