Why is ISRO's GSLV rocket nicknamed 'naughty boy'?

The Indian Space Research Organisation (ISRO) is set to launch EOS-05, an advanced Earth observation satellite, aboard the GSLV-F17 mission from Sriharikota on Friday. The Geosynchronous Satellite Launch Vehicle (GSLV) has often run into problems and has therefore been dubbed the 'naughty boy' of India's space agency. Of its first 18 flights, six failed to achieve full mission success.