Where Did Nitpicker Come from?

Nitpicking is a term, first used in 1956, that describes the action of giving too much attention to unimportant detail. A person who nitpicks is termed as a nitpicker. The terminology originates from the common act of manually removing nits (the eggs of lice, generally head lice) from another person's hair.

Who is a nitpicker?

a person given to harsh judgments and to finding faults. a tiresome nitpicker who seems to think that I can't do anything right.

Is it OK to say nitpick?

Johnson is encouraged to proceed with his nit picking.” ... Although these terms were often hyphenated or written as two words in the past, “nitpick,” “nitpicker,” and “nitpicking” are usually single words today.