It’s not entirely clear when the phrase ‘going overboard’ took on its figurative meaning but it was first cited in the 1930’s buy New York writer Damon Runyon, which makes sense. To associate extreme enthusiasm for something with abandoning ship fits his world perfectly. Basically ‘going overboard’ means risking economic, domestic or social suicide. In the world of fast living that the author wrote about it was par for the course. But it’s certainly not recommended.