Looking for information on the origins, history etc of the following WWI song (lifted from "Oh What a Lovely War!"):

It was Christmas DAy in the Cookhouse
The happiest day of the year.
Men's hearts were fully of gladness
And their bellies full of beer.
When Up old Private Shorthouse,
His face as bold as brass,
Saying we don't want your Christmas Pud,
You can stick it up your...[Chorus}Tidings of Comfort and Joy ...

It was Christmas Day in the Harem,
The eunuchs were standing round,
And hundreds of beautiful women,
Were stretched out on the ground.
When in comes the Bulbat (??) sultan
And gazes on his mighty halls,
Saying what do you want for Christmas Boys?
And the eunuchs answer ... [chorus} Tidings of Comfort...