Is Plunge a Real Word?

1 : to leap or dive suddenly She plunged into the water.

Is plunge up or down?

plunge | Intermediate English

to move or fall suddenly forward, down, or into something: [ I ] Her car plunged off the cliff.

Where does the word plunge come from?

plunge (v.)

late 14c., plungen, "to put, throw, or thrust violently into; immerse, submerge," also intransitive, from Old French plongier "plunge, sink into; plunge into, dive in" (mid-12c., Modern French plonger), from Vulgar Latin *plumbicare "to heave the lead," from Latin plumbum "lead" (see plumb (n.)).