I know “plomb” as having to do with lead, and when I used “with aplomb” the other day I wondered whether the “a” was “opposite ‘a'” as in “amorphous,” such that the positive connotation would be “not lead-y,” so sort of “with lightness.” But this is even better: it’s perpendicularity! I will take it…let’s all be self-possessedly perpendicular when we can.
interlexionality 