Kudos comes from ancient Greek κύδος, kudos, (fame, fame). Giving "kudos" to another is done to appreciate it. Typically, these "virtual presents" are awarded by giving +1 (positive) or -1 (negative). Kudos is singular, but in practice it is often used as a plural form. Therefore, the term "kudo" is often used as the singular form. Under the influence of the American, which has been used for a long time (already in the 90's), it has become more common in the Netherlands in recent years (after about 2005) as part of social bookmarking.
Many web sites (for example, Dumpert and GeenStijl) use the term for user reviews. Also with the Strava mobile application, it is possible to assign each other kudos for accomplished sports performance.
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