dauphin
Concise Oxford English Dictionary © 2008 Oxford University Press:
dauphin /ˈdɔːfɪn, ˈdəʊfã/
▶noun historical the eldest son of the King of France.
– origin Fr., from the family name of the lords of the Dauphiné, ult. a nickname meaning ‘dolphin’.
'dauphin' also found in these Oxford entries:

