Google ___ Viewer (tool for charting word frequency over time)

The answer to this crossword question is “NGRAM“. The clue describes a tool for charting word frequency over time, which is called the Google ___ Viewer. The missing word can be filled in by knowing that Google has a tool called Google NGRAM Viewer, which allows users to search and plot the frequency of words or phrases in a corpus of books over time. This tool is useful for understanding changes in language usage and cultural trends, making it particularly valuable for historians and linguists. With this knowledge, the answer to the crossword clue is NGRAM.