Guj: જામનગર jāmanagara
‘City of the Jam Dynasty’ – City/District, Gujarat
Nawanagar. From Jam (dynasty) and Skt: nagar, ‘city’.
Jamnagar was founded as Nawanagar [Skt: nawa, ‘new’; and Skt: nagar, ‘city’] by Jam Rawal in 1540 as the capital of the Princely state with the same name and one of the most important in the region of Halar.
The development of the modern city was initially undertaken by Jam Ranjitsinhji, Maharaja of Nawanagar 1907-33 (previously he had played test cricket for England, first-class cricket for Cambridge University and county cricket for Sussex). His nephew, Jam Saheb Shri Digvijaysinhji Ranjitsinhji, continued the work in the 1940s.
Nawanagar was one of the first princely states to join Indian Republic in 1948, joining the new state of Saurashtra in 1949. It was renamed, after the Jam dynasty, in 1959 and joined the new state of Gujarat in 1960.
Jam Saheb is a title given to the ruling prince of the Jam Jadeja clan (who variously claim Persian or Rajput origins); jam meaning the ‘brave’, ‘devoted’ or ‘distinguished’ one rather than a strawberry conserve, traffic problem or musical collaboration.

Jam Ranjitsinhji c. 1900 -studio portrait