No, it might not be ethical. Such a description can be seen as objectifying and disrespectful to others. Literature should promote positive values, and this kind of plot might make some readers uncomfortable or give a wrong message about how to view others in a relationship context.
It could be a story where the wife, out of curiosity perhaps, secretly observes a stranger who has some notable physical feature, in this case 'big dick'. Maybe she's at a public place like a beach or a park and she notices this stranger and starts to spy on his actions out of pure intrigue.
There's no way to tell if the 'big dick wife story' is popular just from this name. It could be a very niche story that only a few people know about, like a family - passed - down anecdote or something created within a small community. Or it could potentially be part of a new and emerging trend in some online or offline community, but again, more information would be needed to say for sure.
I'm not sure specifically which 'big dick wife story' you're referring to as there could be many fictional or personal anecdotes with such a name. It could potentially be a made - up story within a certain group or community, but without more context, it's hard to say exactly.
We should avoid this kind of vulgar topic. There are so many other wonderful topics related to strangers, such as the first time a stranger gave you a warm smile that brightened your day.
No, it's not appropriate. Such topics are vulgar and disrespectful to a relationship. A healthy relationship should be based on mutual respect, love, and positive values, not on such inappropriate and objectifying obsessions.
One possible 'big dick for wife story' could be about a husband who surprises his wife with a grand romantic gesture that shows his big heart rather than a literal interpretation. For example, he plans an elaborate vacation to a place she has always dreamed of going. It's a story of how his love in a big way (like the concept of 'big dick' in a non - vulgar sense) makes her feel special and loved.