In one embodiment, a method includes receiving a plurality of search queries comprising n-grams; identifying a subset of the plurality of search queries as being queries for visual-media items based on one or more n-grams of the search query being associated with visual-media content; calculating, for each of the n-grams of the search queries of the subset, a popularity-score based on a count of the search queries in the subset that include the n-gram; determining popular n-grams, wherein each of the popular n-grams is an n-gram of the search queries of the subset of search queries having a popularity-score greater than a threshold popularity-score; and selecting one or more of the popular n-grams for training a visual-concept recognition system, wherein each of the popular n-grams is selected based on whether it is associated with a visual concept.