Everybody , believer and unbeliever alike is familiar with the term " the prodigal son" or the more concise " the prodigal". If you asked, most would probably volunteer that they could define the term prodigal. If they were familiar with Jesus' parable and based on its more salient points, they might define prodigal as repentant. Or they might say that prodigal means returning after a long absence. Or maybe prodigal doesn't describe the son so much as the father's feeling for him as in beloved son or favored son. These would be good guesses. They would also be wrong.
The definition for prodigal is excessively wasteful. How that inept title that has so little to do with a beautiful story depicting a father's great and merciful love towards his wayward son has stuck and even become part of the secular vernacular is as puzzling to me as it probably now is to you.