To tank meaning :
(Informal) To suffer a sudden decline or failure: The stock market tanked yesterday. (The Free Dictionary)
is a quite recent usage:
to tank ( Etynonline)
- Meaning "to lose or fail" attested from 1976, originally in tennis jargon, specifically in an interview with Billie Jean King in "Life" magazine, Sept. 22, 1967:
"When our men don't feel like trying," she says, "They 'tank' [give up]. I never tanked a match in my life and I never saw a girl do it. The men do it all the time in minor tournaments when they don't feel like hustling. You have to be horribly competitive to win in big-time tennis."
Sometimes said to be from boxing, in some sense, perhaps from the notion of "taking a dive," but evidence for this is wanting.