WSJ: Mueller 'Impanels' Grand Jury
Impanel shot to the forefront of our lookups on August 3rd, 2017, following a report in the Wall Street Journal on Robert Mueller's impaneling of a grand jury.
Special Counsel Robert Mueller has impaneled a grand jury in Washington to investigate Russia’s interference in the 2016 elections, a sign that his inquiry is growing in intensity and entering a new phase, according to people familiar with the matter.
—Del Quentin Wilber and Byron Tau, The Wall Street Journal, 3 Aug. 2017
Impanel ("to choose people to serve on a jury") comes from adding the prefix im- to the existing noun panel. The earliest sense of panel, in our records, is defined as "the whole group of persons so summoned from which the jury is selected." The sense of panel referring to a section of something (usually flat) comes from the same source, but developed later.
The word is occasionally spelled empanel, and has a large number of other variant spellings (impaneled/impanelled, empaneled/empanelled, impaneling/impanelling, empaneling/empanelling); so long as you throw together some assembly of ems or ims with some verb endings you have a better than average chance of spelling it correctly.
And yf the same atteynt thenne or ony other tyme happe to remayne vntaken for or by defawte of Iuriours by chalenge or otherwise that vppon euery tales graunted the sayd Mayr and aldermen shall impanell the sayd persones whiche were certified by the sayd aldermen or theyr deputyes and omytted out of the sayd panell or putte theryn other persone or persones beynge cytezyns of the sayd cyte....
—Anno Xi Henrici vij Statuta Bonu[m] Publicum Concernentia Edita in Parliamento , 1500