Although this word (derived simply from the Greek for "youth" and "fear") and the condition it describes may sound rather comical, if taken to extremes or invoked inappropriately it can lead to serious sociological and societal problems and inter-generational conflict.

The term was formulated as recently as 1994 by Kirk Astroth, but the phenomenon is an old one. An irrational fear of youth was manifested even in apparently rational early civilisations like the Greeks and Romans.

In more recent times, this fear has been associated with gang culture, with the media not helping in stoking up a degree of hysteria. This more modern manifestation is not unconnected to the rise of the teenager as a distinct demographic, which in some ways has led to youth being more empowered, but has also caused hostility in some quarters.

It can have ramifications beyond a (perhaps understandably!) frustrated adult having an occasional rant at stroppy adolescents, and can be deleterious both to young people themselves (many countries now have low ages of criminal responsibility) and older people who feel they have to be prisoners in their own homes.

More Info: en.wikipedia.org