From the Algonquian for "little turtle." Brought into the English language circa 1672.
According to Cirlot's Dictionary of Symbols:

"The turtle has a variety of meanings, all of which are organically related. In the Far East its significance is cosmic in implication. As Chochod has boserved: 'The primordial turtle has a shell that is rounded on top to represent heaven, and square underneath to represent the earth.' To the Negroes of Nigeria it suggests the female sex organ and it is in fact taken as an emblem of lubricity. In alchemy it was symbolic of the 'massa confusa". These disparate sense have, nevertheless, one thing in common: in every case, the turtle is a symbol of material existence and not of any aspect of transcendence, for even where it is a combination of square and circle it alludes to the forms of the manifest world and not to the creative forces, nor to the Origin, still less to the irradiating Centre. In view of its slowness, it might be said to symbolize natural evolution as opposed to spiritual evolution which is rapid or discontinuous to a degree. The turtle is also an emblem of longevity." (p. 353)

The Encyclopedia of Religion has an entry on Turtles and Tortoises--here's an excerpt:

"There is a widespread belief that the earth rests on the back of a turtle or tortoise. This archaic idea is found not only among North American Indians but also in South Asia and Inner Asia. The turtle now appears even as a symbol of the entire universe (e.g. in China). Moreover, according to creation myths involving an earth diver, the turtle, sometimes as an incarnation of the divine being, plays a prominent part in the cosmogony of various cultures." (v. 15, p. 96)

Other resonances occur: the naming of the North American continent as "Turtle Island" by the Native Americans; and the use of the terrapin as a character in the Uncle Remus tales of Joel Chandler Harris.