What does "easy peasy" mean — and why is it funny?

informal, playful

Meaning

Extremely easy; requiring no real effort at all.

Where it comes from

A playful rhyming phrase, popular with children, often extended to 'easy peasy lemon squeezy', possibly from an old British advert.

Why it is funny

The humor is pure sing-song silliness. The phrase rhymes for no reason other than fun, and saying it makes a difficult-sounding task collapse instantly into something childish and light.

Used in a sentence

"Setting up the new phone was easy peasy."