A fool's paradise

Meaning

A state of happiness based on false hope.

Origin

This is an early phrase, first recorded in the Paston Letters, 1462:

"I wold not be in a folis paradyce."

Shakespeare later used it in Romeo and Juliet, 1592.

Nurse:
Now, afore God, I am so vexed, that every part about
me quivers. Scurvy knave! Pray you, sir, a word:
and as I told you, my young lady bade me inquire you
out; what she bade me say, I will keep to myself:
but first let me tell ye, if ye should lead her into
a fool's paradise, as they say, it were a very gross
kind of behavior, as they say: for the gentlewoman
is young; and, therefore, if you should deal double
with her, truly it were an ill thing to be offered
to any gentlewoman, and very weak dealing.

See other phrases and sayings from Shakespeare.