The article of New York Times (May 2) titled “Biden shares tales of loss with military families” quotes the line in Joe Biden’s 2007 memoir - “I began to understand how despair led people to just cash it in.”
The Vice President lost his wife and 13-month-old daughter in a car crash in 1972.
The article reads:
“On Friday, Biden told the military families how low the crash had brought him. “I probably shouldn't say this with the press here, but - no, it’s more important - you’re more important,” he said. Biden had actually told the story before, on page 80 of his 2007 memoir, “Promises to keep.” “I began to understand how despair led people to just cash it in,” Biden wrote.”
As I’m unfamiliar with the phrase, “cash it in,” I consulted online dictionaries:
Cambridge Dictionary doesn’t register ‘cash it in’ but ‘cash in on sth‘meaning ‘‘to get money or another advantage from an event or situation, often in an unfair way.’
Oxford Dictionaries registers ‘cash sth in’ meaning ‘convert an insurance policy, savings account, or other investment into money.
Neither of the above definitions seems to be applicable to the above line.
Merriam-Webster doesn’t register ‘cash it (something) in.’
Google Ngram shows the linear increase of the incidence of the usage of “cash it in” since circ 1920.
What does “cash it in” in Mr. Biden’s “I began to understand how despair led people to just cash it in,” mean? Is the phrase, ‘cash it in’ used ofen in this way as a popular idiom?