Anglo-French (n.)

the form of Old French written in England from the Norman Conquest (1066) through the Middle Ages; the administrative and legal language of England 12c.-17c.; the name is attested from 1887 and was popularized, if not coined, by Skeat.

And Frenssh she spak ful faire and fetisly,

After the scole of Stratford-atte-Bowe,

For Frenssh of Parys was to hir unknowe.

[Chaucer]