Evolved from 《史记·郦生陆贾列传》: 「数见不鲜」 — Liu Bang's advisor Lu Jia was told that if he visited too often, his host would no longer serve him fresh meat. Modern 屡见不鲜 keeps the sense: familiarity breeds loss of novelty.
mistakes
鲜 here means 'fresh, novel' (xiān, first tone), not 'few' (xiǎn, third tone). The point is the thing has lost its freshness because it's seen so often.
