The story
From sunlit (“illuminated by sunlight”) + uplands (“areas in the interior of a country with a generally higher elevation”) (evoking a pleasant, happy place), popularized by its use in the “This was their finest hour” speech delivered by Winston Churchill (1874–1965), the Prime Minister of the United Kingdom, to the House of Commons on 18 June 1940: see the quotation.
Etymology from Wiktionary, CC BY-SA 4.0.