Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culturehere. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.
Known as Jandals (Japanese sandals), thongs and chappals elsewhere, I've always called them flip flops, which is a great name. When I looked the word up on Wikipedia some joker had managed to insert the idea that they were invented by Phillipe Phillope!