turtle (n.1)

"tortoise," c. 1600, originally "marine tortoise," from French tortue, tortre (13c.) "turtle, tortoise" (often associated with diabolical beasts), of unknown origin. The English word perhaps is a sailors' mauling of the French one, influenced by the similar sounding turtle (n.2). Later extended to land tortoises; sea-turtle is attested from 1610s.

turtle (n.2)

"turtledove," Old English turtle, dissimilation of Latin turtur "turtledove," a reduplicated form imitative of the bird's coo. Graceful, harmonious and affectionate to its mate, hence a term of endearment in Middle English. Turtle-dove is attested from c. 1300.

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Definitions of turtle from WordNet
turtle (v.)
overturn accidentally;
Synonyms: capsize / turn turtle
turtle (v.)
hunt for turtles, especially as an occupation;
turtle (n.)
a sweater or jersey with a high close-fitting collar;
Synonyms: turtleneck / polo-neck
turtle (n.)
any of various aquatic and land reptiles having a bony shell and flipper-like limbs for swimming;