Turtle
mid 16th century: apparently an alteration of French tortue (see tortoise).
wiktionary
Modification of Middle English tortou, tortu, from Old French tortüe (under the influence of Middle English turtel, turtur(“turtledove”), see Etymology 2 below), from Medieval Latin tortuca (compare Spanish tortuga), the same source of tortoise (see there for more). Displaced native Old English byrdling.
From Middle English turtle, tortle, turtel, turtul, from Old English turtle, turtla(“turtledove”), ultimately from Latin turtur(“turtledove”), of imitative origin.
etymonline
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.
