Douglas Harper's Etymology Dictionary
isles off Cornwall, of unknown origin. Pliny has Silumnus, Silimnis. Perhaps connected with the Roman god Sulis (compare Aquae sulis "Bath"). The -y might be Old Norse ey "island" The -c- added 16c.-17c. "[A]bout the only certain thing that can be said is that the c of the modern spelling is not original but was added for distinction from ModE silly as this word developed in meaning from 'happy, blissful' to 'foolish.'" [Victor Watts, "Cambridge Dictionary of English Place-Names," 2004].\n\n\n
Usage examples of "scilly".
End and the Scilly Isles, Ushant and Cape Finisterre, are projecting features along the middle distance of the picture, and the English Channel recedes endwise as a tapering avenue near the centre.
Stephen answered, adding something or other rather muddled about farewell and adieu to you Spanish onions and the first land called the Deadman and from Ramhead to Scilly was so and so many.
Cornwall, the Scilly and Channel Islands, Ireland and Brittany, are the remains of its highest summits.
Now known as the Scilly Isles, off the southwestern tip of Cornwall, England.
Caligula, who had already informed the Senate of his total subjugation of Germany, now wrote to say that King Cymbeline had sent his son to acknowledge Roman suzerainty over the entire British archipelago from the Scilly Islands to the Orkneys.
I fancy most of us gave a good sigh of relief when at last we were clear of the Scilly Isles.
In the southern west approaches, from the Scillies outwards, the tenders hovered almost constantly.
They are labeled with the names of the cities where they terminate: Faial in the Azores, Brest in France, Bilbao in Spain, Gibraltar 1, Saint John's in Newfoundland, the Isles of Scilly, two cables to Carcavelos in Portugal, Vigo in Spain, Gibraltar 2 and 3.
You are also charged with putting your castle of Holt, in Denbighshire, into a state of defence, with providing it with a strong garrison and stores of war, with fortifying your castle of Sudley, in Gloucestershire, and with possessing yourself of the strong and dangerous Isles of Scilly, to which you purposed to retreat.
Moreover, my lord has two strong castles, Holt and Sudley, the former strongly garrisoned and well stored, and he has the Scilly Islands to retire to in case of need.
Well not quite: Kenneth Sisam (once my tutor) survives in the Scilly Isles, a mere 76.