Google Ngram is a tool that list how often a word appeared in the printed works that Google scanned for it's Google books project.
The page for meritocracy indicates that the first usage was in 1811. From there it was used till 1816 and afterwards relatively forgotten. The word reappears in 1938. Till 1954 almost nobody used the term and it suddenly got a strong boost in 1955.
Did they use it in it's modern meaning? In 1954 Edward Abbey writes in Slumgullion stew:
The new America will be organized along sound military lines. Not an oligarchy as before, hiding behind a facade of democracy, but a hierarchy of power based on merit and ability. Meritocracy. Government of the people, yes. Government for the people, yes. But government by the people? Never again.
A hierarchy of power based on merit and ability is the modern meaning.
From looking at the graph the year 1958 got a little bump but that year isn't very special for the usage of the word meritocracy.
This means the claim by The Atlantic is false.