We investigated a video bookmarking function, which is expected to be useful for students to efficiently review videotaped lectures. Video bookmarking allows students to record classroom lectures and mark the start time of specific points in the lecture video. They can later jump directly to bookmarked segments when reviewing the lecture video. It is important that keywords be useful indicators of bookmarked video segment content. In this study, we conducted a questionnaire survey to evaluate five keywords for bookmark labeling. We evaluated the suitability of the keywords based on subjective evaluation and system usage logs. We conclude that the five keywords examined are suitable for efficient video bookmarking by students during lectures.