Over at the OED, I find that the phrase “a piece of cake” to mean something easily done is in fact very recent (but not quite so recent as I guessed):
Colloq. phr. a piece of cake: something easy or pleasant.
1936 O. NASH Primrose Path 172 Her picture’s in the papers now, And life’s a piece of cake.
1942 T. RATTIGAN Flare Path 1, Special. Very hush-hush. Not exactly a piece of cake, I believe.
1943 P. BRENNAN et al. Spitfires over Malta i. 31 The mass raids promised to be a piece of cake, and we anticipated taking heavy toll of the raiders.
1960 T. MCLEAN Kings of Rugby 205 They took the field against Canterbury as if the match were ‘a piece of cake’.
Of course it was Ogden Nash, my earliest literary crush, who first used the phrase in writing long before I was born. Time, I think, for a short tribute in the form of one of my favorite poems of his, called So Does Everybody Else, but Not So Much:
O all ye exorcizers come and exorcize now, and ye clergymen draw nigh
and clerge,
For I wish to be purged of an urge.
It is an irksome urge, compounded of nettles and glue,
And it is turning all my friends back into acquaintances, and all my
acquaintances into people who look the other way when I heave into view.
It is an indication that my mental buttery is butterless and my mental
larder lardless,
And it consists not of “Stop me if you’ve heard this one,” but of “I
know you’ve heard this one because I told it to you myself, but I’m going
to tell it to you again regardless,”
Yes I fear I am living beyond my mental means.
When I realize that it is not only anecdotes that I reiterate but what
is far worse, summaries of radio programs and descriptions of caroons in
newspapers and magazines.
I want to resist but I cannot resist recounting the bright sayins of
celebrities that everybody already is familiar with every word of;
I want to refrain but cannot refrain from telling the same audience on two
successive evenings the same little snatches of domestic gossip about
people I used to know that they have never heard of.
When I remember some titlating episode of my childhood I figure that
if it’s worth narrating once it’s worth narrating twice, in spite of
lackluster eyes and dropping jaws,
And indeed I have now worked my way backward from titllating episodes
in my own childhood to titillating episodes in the childhood of my parents
or even my parents-in-laws,
And what really turns my corpuscles to ice,
I carry around clippings and read them to people twice.
And I know what I am doing while I am doing it and I don’t want to do
it but I can’t help doing it and I am just another Ancient Mariner,
And the prospects for my future social life couldn’t possibly be
barrener.
Did I tell you that the prospects for my future social life couldn’t
be barrener?