Here’s an example of how the language evolves in unintended ways.
In the last major election, the group that called itself “Swift Boat Veterans” presumably chose that name because they felt it had positive connotations to patriotism and high-minded military service, and would therefore make more believable the nasty political charges they were dishing out.
Instead, the opposite has happened. NYTimes.com reports that the negative tactics of that group have backwashed and destroyed those positive connotations:
“You would not hear the word ‘Swift boat’ and think of people that served their country and fought in Vietnam,” said Jim Newell, who spent a year as an officer in charge on one of the small Navy vessels in An Thoi and Qui Nhon. “You think about someone who was involved in a political attack on a member of a different party. It just comes across as negative. Everyone who is associated with a Swift boat is involved in political chicanery.”
This is why using euphemisms never works. You can’t use a harmless sounding word in place of a dirty word because the harmless word will eventually become dirty, and it will still sound dirty even when it’s used in its former harmless context.
The only way I know to avoid this trap is to choose your words based on how accurately they fit the idea you’re expressing, and ignore the connotations. For instance, “dooky” is not less offensive than “shit” because they have identical meanings, but “dooky” sounds less offensive to a shallow and juvenile mind.