Other forms: plummeted, plummeting, plummets
To plummet is to fall suddenly and very fast. Prices plummeted, plummet to the ground, plummeting temperatures.
It is used far more of numbers than of objects now — sales, temperatures and share prices plummet daily in the press. The noun is a lead weight on a line, which is the image: a plummet drops straight down. Note plumb, plumber and plumb line, all from the Latin for lead.
1verbplummetTo fall suddenly and very fast.
“The temperature plummeted overnight, and by morning the lake had frozen.”
plummet is a steep fall.
Old French plommet is a small lead weight, from Latin plumbum, lead. Plumber, plumb and aplomb come from the same lead.
Latin
plumbum — lead
Old French
plommet
Middle English
plommet — ball of lead, plumb of a bob-line
English, today
plummet
Built from
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.
Etymology from Wiktionary, CC BY-SA