Harpic

noun2

1. •
   An international brand of toilet cleaner

   • ‘HARPIC’ CLEANS THE TRAP & PIPE. Weekly sprinkling KEEPS the BOWL SPOTLESS. — 1923
2. •
   (slang) Crazy, insane (from the Harpic marketing slogan ‘cleans round the bend’)

   • “Harpic? […] Why do you call him that?" "He's clean round the bend." — 1951