i Register
In some senses, diddly is marked as informal, slang. Watch for register when choosing this word.
noun
A small amount of no worth.
They head down the mountain, back to base camp, and when they get there they don't say diddly. They don't talk. Not a word, like they're deaf and dumb.
intj
A written representation of a trill sound.
On the handcar mornings or evenings he would amuse his companion by pumping away to a triple-tongued pattern, which he would hum emphatically as they rolled along: "dum diddly diddly diddly diddly diddly diddly dee dee-dum dum diddly diddly diddly diddly diddly diddly dee..."
...When combined with the following picked note, this gives a rhythmic 'diddly-dum' effect.
noun
penis
"My child is going to be taught all about sex as soon as he can understand. Mother-in-law is always clucking to him about his diddly. No, no, I say, you must call it penis."