Low-down vs lowdown as noun vs adjective

Question

In an online CPE mock test I was given this question:

• The princess's nanny's autobiography really gives the ____ on the life among the royals.

The correct answer was "low-down" which I did choose.

But I'm having a trouble understanding why an "adjective-spelled" word is used in place of a noun.

I might be wrong, but "low-down" is an adjective that means: mean or unfair whereas "lowdown" is the noun that means: relevant information.

Is there no difference between spelling this word with a hyphen or without one?

Answer 1

Looking at this Ngram graph, it seems that there is some variation in the spelling of the noun form. While it is true that the majority of usages are unhyphenated, currently about 15% of instances are hyphenated.

The word only came into use in 1920 and, between then and 1960, both spellings were in equal use. I guess that it was first put into a dictionary at that point, and from then on the dictionary (unhyphenated) form has grown progressively stronger.

Hyphenation is generally regarded as a form of punctuation, and as such there is a lot more flexibility than there is with the actual letters in a word.