Early 20th century; earliest use found in Elinor Glyn (1864–1943), novelist and screenwriter. From French truite bleue, lit. ‘blue trout’ from truite + bleue, feminine of bleu.
Definition of truite bleue in US English:
truite bleue
(also truite bleu)
nountruːˌiːt ˈbləː
Truite au bleu.
Origin
Early 20th century; earliest use found in Elinor Glyn (1864–1943), novelist and screenwriter. From French truite bleue, lit. ‘blue trout’ from truite + bleue, feminine of bleu.