Plural of aplomb; instances of confidence, self-assurance, and composure, or weights/plumb lines used in measurement.
From French 'aplomb' (equilibrium, confidence), derived from Latin 'ad plumbum' (to the plumb). The plural marks multiple instances of this quality or tool.
The original French meaning was literally about being 'at the plumb line'—perfectly balanced—which is why it came to mean perfect self-assurance, since a confident person is psychologically balanced!
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