hidey-hole or hidy-hole/ʹhiedi/ noun

• backswing
• back to/at square one
• back to back
• back-to-back
• back to front
• back to the drawing board
• backtrack
• back up
• backup
• backveld
• backward
• backwardation
• backwards
• backwards and forwards
• backwash
• back water
• backwater
• backwoods
• backwoodsman
• back yard
• bacon
• Baconian
• BACS
• bacteraemia
• bacteri-