I have been wondering that myself,I'm currently reading the biography of JQA and wikipedia said "Kwinzi" in the int. pron. yes Quinzee is right.

Quincy originally part of Dorchester ,then given to Braintree as North Braintree where John Hancock,John Adams and John Q Adams were all born.

Then broke off as the city of Quincy but not named as one would think after JQA but after Colonel John Quincy.

​

I had always thought the towns of Adams /North Adams was named for John Adams but the town originally known as East Hoosac was actually named for Samuel Adams.And Adams and NA split during the industrial revolution.