The only thing I can find is, there was a character in a popular fantasy series that was written beginning in 1970
http://en.wikipedia.org/wiki/List_of_Chronicles_of_Amber_characters
Maybe the character name contributed to exposure and made it seem more usable to people. But IMO, usually, pop character-names suit fashions that are already in the process of becoming.
Daryl was being used as a feminine name occasionally (actress
Daryl Hannah was born 1960), as was
Dale - and
Dara sounds a lot like
Tara (both usually had the AIR sound in the US) too. A bunch of "Dare" names were in fashion during the same period:
http://www.behindthename.com/top/name/dara,daryl,darren,darrell,darryl
- mirfak