I once fed my dog a bowl of cooked polenta, after I’d run out of regular pet food. It gave her the runs, so I’d assume it could be used to treat constipation in humans.
Welcome 
That does sound like it’s the right thing- a bowl of what’s basically bland custard does sound like a pretty reasonable sick person food. At least for those not lactose intolerant.
I remember my mother making a thin custard with cornstarch for my baby sister. It must have been around 1958, in Denmark.
My mother used to make it for my grandmother, who was bedridden for many years. This would be in the UK in the 1960s. It was as has been described, a sort of milky custardy pudding, easily digestible for invalids.
Before chocolate began to give me instant stomach aches, I used to make “Castilian Hot Chocolate” which was milk, cocoa powder, cinnamon, sugar, and cornstarch aka cornflour whisked together over heat. Turns out somewhere in between hot cocoa and chocolate pudding and very good.
The Cornflower, also known as Bachelor’s Buttons, is a tall wispy annual with a true blue flower, hence the color name Cornflower Blue. Its latin name is Centaurea cyanus, and the name cornflower comes from it being a common grain field weed (corn is the general Briitish term for grain).
Cornflower can be used to color food blue, too. At least, it’s recommended by Pieometry.
“Corn flour” always sounds odd to me, because I expect it to be corn meal, not corn starch. I use both regularly in the kitchen, and corn meal is more like flour in how it’s used. (although corn starch looks more like wheat flour, I suppose.)
When we’re discussing “corn flour” in the Agatha Christie era, are we talking about corn as in maize, or the older definition of corn as “grain,” which in England would probably have been wheat?
https://www.straightdope.com/21341268/how-could-the-romans-use-corn-it-s-american
It would have been maize- wheat flour would just have been called ‘flour’.
Corn is used in England (or was used, the use does seem to be on the way out, thankfully) in a generic sense to mean grains, but it’s also used as a specific term for maize- we can usually tell which it is by context. Usually.
But “corn flour” isn’t just ground corn, it’s corn starch.
Manufacture[edit]
The corn is steeped for 30 to 48 hours, which ferments it slightly. The germ is separated from the endosperm and those two components are ground separately (still soaked). Next the starch is removed from each by washing. The starch is separated from the corn steep liquor, the cereal germ, the fibers and the corn gluten mostly in hydrocyclones and centrifuges, and then dried. (The residue from every stage is used in animal feed and to make corn oil or other applications.) This process is called wet milling. Finally, the starch may be modified for specific purposes.[14]
I have no idea what your point is here. I know it’s not ground maize, that wasn’t the question- the question was if it could really be wheat flour, and the answer is no.
I mean, I’m English- I have this stuff in the cupboard.
Okay, i just have misunderstood the post. I read it as “if it were wheat flour, rather than maize flour…”
I have the stuff in my cupboard, too. Only the label is “corn starch”, because I’m American.
Just to add an extra option to the discussion, to me the description of the dish sounds like Kisiel - you can use any starch, mix it with fruit juice, and heat until thickened. No milk, no gluten, just sweet transparent gloop. It used to be a popular dessert when i was growing up in eastern Europe, and features as an acceptable meal for a person with stomach ulcers in a book from my childhood.
I’ve had kisiel in Russia. It’s similar to Jell-O.
Potato starch in China in my experience. Used identically as we use corn starch here. Both as a thickener for sauce and as a coating on meats before deep frying for a light crust.
I know I’m reviving a zombie 
, but I can offer another reference to this substance. In On the Beach, written in 1957 by Australian engineer/novelist Nevil Shute, an older female character who’s developed radiation sickness asks her adult son to bring her “a cup of cornflour” (no hyphen). I seriously doubt she was asking for a cup of a dry powdered thickener, so there must have been a beverage-like application for it.