So I'm digging into the history of Ireland's relationship with coleslaw. I'm approaching it with an open mind but early indications are that chilled foods rose in popularity around the time that a fridge was a status symbol:
(from 1954)

We might not love rhubarb prune crisp or asparagus on toast anymore, but coleslaw is here to stay.

But does anyone make it with sugar and pineapple juice anymore?
(from 1947)

The Belfast Newsletter in 1942. The Ministry of Food tips its cap to the UK's new wartime allies, celebrating American grub like pumpkin pie, baked beans and coleslaw.

This is one of the earliest mentions in a newspaper on the island of Ireland....

Lasagne and coleslaw both became popular in the 1970s with the arrival of delicatessens and the trend of serving them together appears to have its roots in this coincidence.

A 1977 recipe for lasagne by Georgina Campbell suggests coleslaw as a side as the ingredients for a green leafy salad would not have been in season.

This lasagne recipe (with chicken livers, pork and milk) is from @irishexaminer 1985.
"Serve with coleslaw" is the last line - the idea of a green salad isn't even entertained.

As always, our food culture is a keyhole that, when peeped into, reveals our relationships with the environment, technology leisure time and war.

"Nutritionally [lasagne] is a fairly complete meal, particularly if accompanied by a green salad or coleslaw".

But at what point did serving coleslaw with lasagne become seen as a country thing?

This is from Orna Mulcahy in the @IrishTimes in 1999.

In 1996 a letter writer from Sandycove asked the editor of the Irish Times why the country was so obsessed with coleslaw.

1996 also saw a public panic over whether or not it was safe for pregnant people to eat coleslaw.

Nowadays that adds to a foodstuff's prestige (sushi, smelly cheese, paté, whiskey) but it didn't help coleslaw. In Dublin anyway.