Plunge means to jump, fall, or push something suddenly and forcefully into water or another substance. It can also mean to move or be pushed quickly into a difficult situation or a lower level.
From Middle English *plungen*, from Old French *plongier*, from Vulgar Latin *plumbicāre* “to sink by means of lead,” related to Latin *plumbum* “lead.” The idea again comes from a heavy object being pushed or falling into something.
English uses *plunge* both for water and for life choices: you can plunge into a lake or plunge into a new career. That shared verb suggests that risk, depth, and commitment feel emotionally similar to us.
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