It started in the Scottish Borders town of Selkirk with local menace Dr Crack, initially referring to being desirous of being sacked from her job. The actual name of the employer is unknown to scholars, who point to a variety of nicknames, such as; The Death Star, Arse Factory and Soul Toilet.
The true identity of Dr Crack is also a mystery to academics, due to the number of alternate nicknames bandied about.
The word has, as previously said, evolved into meaning all of the little things that make life bearable for the working stiff. A night in the pub could definitely be sackage, as could a good book, friendship, or even simple pleasures like stuffing oneself full of junk food additives at lunchtime and buzzing one's way through a dull afternoon at work.
The antonym for sackage would almost certainly seem to be bawbaggery.
That beer was pure sackage.
It's all about the sackage.