It's almost certainly a story he picked up somewhere. It's the kind of folk myth that still gets invented today about past wars. Herodotus traveled around to collect stories for his history and it's more likely many of the fanciful tales he tells were stories related to him by others rather than things he solely made up on his own.

Herodotus spends too much time casting judgement on some of the stories he tells, explaining which ones he thinks are true or false and why he thinks that, to be a mere fanatic for narrative.