Also of interest is that sometimes it is hyphenated, sing - around or even double hyphenated sing - a - round. Back in Woolwich in thw 70s I used to drink with a load of irish and scotch builders in the Bull pub. On a Monday afternoon they used to have a huge singaround in the bar. If anybody didn't sing when it got to their turn Then they bought-a-round of drinks for everybody! - quite expensive as there was usually between 15 and 20 in the company. Sometimes the rules were tightened up so that if you hesitated or got the words wrong then you forfeited!