New London is 355 years old, but its name is only 343 years old. It took more than a decade of effort by the settlers to get the Legislature to agreed to naming the plantation New London. The early settlement went by various Indian names, such as Pequot or Nameaug. In 1648, the inhabitants selected London as their name, but the General Court baulked, probably thinking that the little settlement was being a bit presumptuous. The Court suggested the more modest name of Fair Harbor. The settlers spurned this suggestion.

Frances Manwaring Caulkins, in her classic history, writes that the settlers wanting their plantation to be called London

... was no suggestion of vainglory, the result of a high-wrought expectation of rivaling the metropolitan splendor of Great Britain; but a very natural mode of expressing their deep-rooted affection for the land of their birth.

In 1658, the Legislature relented and finally passed an act legalizing the name of New London. The addition of the word "New" suggests a compromise. The act read:

Whereas it hath been a commendable practice of the inhabitants of all the colonies of these parts, that as this country hath its denomination from our dear native country of England, and thence is called New England; so the planters, in their first settling of most new plantations, have given names to those plantations of some cities and towns in England & This court considering, that there hath yet no place in any of the colonies, been named in memory of the city of London, there being a new plantation within this jurisdiction of Connecticut, & it being an excellent harbour and a fit and convenient place for future trade, it being also the only place which the English of these parts have possessed by conquest & that therefore, they might thereby leave to posterity the memory of that renowned city of London, from whence we had our transportation, have thought fit, in honor to that famous city, to call the said plantation New London.

Changing the name of the river upon whose banks the city stands to Thames was apparently a logical next step. Previously the river, like the city, has flowed with various English and Indian names. Although she does not say exactly when the name was changed to Thames (prounced with the "Th" and not, as the English do "Temes"), Caulkins lists several of its previous names:

Frisius, Great, Great River of Pequot, Little Fresh, Mohegan, New London, Pequod or Pequot.

The Thames begins in Norwich and runs some 15 miles to where Fishers Island and Long Island Sounds meet. Actually, the Thames isn't a river. It is an estuary of the sound.