What's the meaning of the phrase 'Easy-peasy'?
Easy-peasy means very easy and simple, mostly used by children and sometimes elongated to 'easy-peasy lemon squeezy'.
What's the origin of the phrase 'Easy-peasy'?
The expression 'easy-peasy' appears to be American in origin. At least, the first example of it that I can find in print with the 'very simple' meaning is from the Cincinnati Enquirer, January, 1953:
There's a brief air travelogue of highlights of a jet trip from London to Cairo in around three hours - a distance requiring days and days by ground travel. The flight is such an easy-peasy affair for the air travellers, they seem to be motionless in a fantastic and lovely, sun-drenched cloudland.
Whoever coined the espression may have been influenced by the earlier American phrase as easy as pie. It may also be derived from another US term 'easy-breezy' which had been used to desribe casual clothing since the late 19th century and to mean 'uncomplicated' since at least 1948.
The phrase didn't catch on and doesn't appear widely in US sources until the late 1970s. It did cross the Atlantic though, unless this following example is an independent coinage - a piece published in English newspaper The Guardian, in June 1983:
Chap comes in, sits down, says, "I want to be a marine biologist." Easy peezy lemon squeezy. Careers master looks up the best universities, suggests the right colleges, flushes out the appropriate courses.
Note that that also seems to be the first recorded use of the extended form 'Easy-peasy, lemon squeezy'.
We ought not to finish without dispelling a folk-etymology myth, that "Easy-peasy lemon squeezy" originated as a slogan for Sqezy washing up liquid.
Sqezy certainly was washing up liquid, marketed in the UK by the Domestos Company in the 1950s.
This advert was part of a concentrated campaign in the summer of 1957 to encourage the good people of Birmingham England to buy the product. It was published in The Birmingham Post newspaper in large half-page spreads many times in June/July 1957. It must have had some effect. I'm from Birmingham and my parents took the paper. I can recall using the stuff in the 50s in the 'washing up equals pocket money' deal I had with my mother. I don't recall it being especially easy - it was just detergent after all.
As far as the folk-etymology goes, Domestos never used "Easy-peasy lemon Sqezy" as a slogan for Sqezy and it didn't smell of lemons.