Final answer:
The repetition of 'no stir' in "Inchcape Rock" underscores the calmness of the sea, setting a tone of stillness that contrasts with the later revealed potential for danger.
Step-by-step explanation:
The repetition of the words "no stir" in the first line of the poem "Inchcape Rock" is a literary device used to emphasize the calmness of the sea. This repetitive phrase sets the tone for the poem by illustrating a very still and placid ocean scene, which is entirely devoid of any movement or turbulence. The effect is to contrast the current peacefulness with the potential for danger and drama that the poem later reveals, hinting at the treacherous nature of the seas around the Inchcape Rock.