An idol is an object of worship. The word functions only as a noun. Idle has several definitions, including (1) inactive, (2) to pass time without doing work, (3) to run (a motor vehicle) while out of gear or not in motion, (4) to make inactive, and (5) a state of idling. It’s usually an adjective, but senses two, three, and four make it a verb, and sense five makes it also a noun.
There’s also the rarer idyll, which refers to (1) a tranquil natural scene, (2) a carefree episode, and (3) a short, pastoral poem. This word is also not to be confused with ideal.
Other than their similarity in sound and pronunciation, the three words have nothing in common. Idle has Germanic roots and is documented in English (Old English, to be precise) as long ago as the ninth century. Idol goes back to the Latin idolum, which in turn comes from a corresponding Greek word. Idyll derives from Latin and Greek words for short, descriptive poems. Idol and idyll are much newer in English than idle; idol entered the language around the 14th century, idyll a couple of centuries later.
Aguilera was a long-time admirer of James, and paid tribute to her idol by singing James’s signature song “At Last.” [Wall Street Journal]
She warned that a “middle-class terror” of raising fat and idle children has led to an unfair perception of gamers as sedentary. [Telegraph]
New arrivals prefer the noise and commotion of the road to the idyll beyond. [Economist]
The motor was only idling for the final 100 metres, making the final section more impressive. [Sydney Morning Herald]
The park also features relics from Egyptian idol worship as well as interpretive signs about ancient copper mining. [WND]
The sheep seem pretty idyllic themselves: polite little nibblers who only sometimes block the road. [New York Times]