This is old feature I liked ...
Google comes with other this feature named Sets Live since 2008.
Based on an idea to be able to recognize the similarity of a set of terms.
It's worked on spreadsheet and is very simple.
Just fill with two words in the spreadsheet, select with key SHIFT (highlight the two cells).
Press CTRL key and dragging the small blue box and google will automatically identify other similar terms.
Also seam Google continues to work on expanding their use of semantic information.