Pacific

On September 20, 1519, Magellan and a crew of 270 men set sail from Spain on their around-the-world voyage in five small vessels including his flagship Trinidad,Concepcion, San Antonio, Victoria, and Santiago. It took the fleet, or at least the three remaining ships in the fleet, 38 days to navigate the strait around South America that was to bear Magellan’s name. During the last week of November, the fleet emerged into what Magellan described as a “beautiful, peaceful ocean.” Thus, it was named the Pacific Ocean (“pacific” meaning “peaceful.”)

Arctic

The name derives from Greek Mythology, where it means the “Sea of The word Arctic comes from the Greek ἀρκτικός (arktikos), "near the Bear, arctic, northern"[6] and that from the word ἄρκτος (arktos), meaning bear.[7] The name refers either to theconstellation Ursa Major, the "Great Bear", which is prominent in the northern portion of the celestial sphere, or to the constellation Ursa Minor, the "Little Bear", which contains Polaris, thePole Star, also known as the North Star.

Indian ocean is obviously named after India.

Atlantic ocean is named from the greek “sea of Atlas”