[mapt]

These are two very different systems. It's interesting that they ended up sharing a name in different locales.

Usually "Tontine" is used for a retirement plan that people pay into, which distributes the dividends evenly among the surviving cohort of investors; The last survivor gets the whole pot of investment. They fell into disrepute in small part for having salacious incentives to murder each other as the number of survivors drops, but mostly for being in competition with life insurance, pension, mutual funds, and later tax-incentive-investment-account models that ended up being more favored by governments & finance.

What you're describing is what I know as a 'tanda'.

https://en.wikipedia.org/wiki/Rotating_savings_and_credit_as...

https://en.wikipedia.org/wiki/Tanda_(informal_loan_club)