plummet

Etymology

From Middle English plommet (“ball of lead, plumb of a bob-line”), recorded since 1382, from Old French plommet or plomet, the diminutive of plom, plum (“lead, sounding lead”), from Latin plumbum (“lead”). The verb is first recorded in 1626, originally meaning “to fathom, take soundings", from the noun.

noun

1. (archaic, nautical) A piece of lead attached to a line, used in sounding the depth of water; a plumb bob or a plumb line.
2. (archaic) Hence, any weight.
   His parachute was shot half away, and if he'd jumped he would have fallen like a plummet. 1945, Ernie Pyle, Here Is Your War: Story of G.I. Joe, The World Publishing Company, page 93
3. (archaic) A piece of lead formerly used by schoolchildren to rule paper for writing (that is, to mark with rules, with lines).
4. A violent or dramatic fall.
5. (figurative) A decline; a fall; a drop.
   Yet another seriously under-par performance is unlikely to provide any real answers to their remarkable plummet in form - but it proves they can at least churn out a much-needed result. December 29, 2010, Chris Whyatt, “Chelsea 1 - 0 Bolton”, in BBC

verb

1. (intransitive) To drop swiftly, in a direct manner; to fall quickly.
   After its ascent, the arrow plummeted to earth.
   Some speculated Twitter’s stock would plummet, while another said the company would not have to be owned by “a moron,” using an expletive to refer to Mr. Musk. 2022-10-04, Kate Conger, Lauren Hirsch, “Elon Musk Suggests Buying Twitter at His Original Price”, in The New York Times, →ISSN
   Passenger numbers had been rising sharply. But the replacement of the services by buses, which take far longer because of the number of stations in out-of-the-way villages on the route, will ensure they plummet again. December 14 2022, Christian Wolmar, “No Marston Vale line trains... and no one in charge seems to 'give a damn'”, in RAIL, number 972, page 46