An idealised place that is nowhere.
The name is a pun - ’eu’ is the Greek prefeix meaning ‘good’ (eudemonia - the good life, eucalyptus - the good covering, euthenasia - the good death, etc.)
Topos is place
eutopia - the good place.
u (ou) - is ’not’ in Greek (indicates negation)
u-topia - the (good) place which is not a place.