Later Anglo-Norman is conventionally portrayed as moribund, isolated from the mainstream of French, and extensively calqued on English. This study demonstrates that in the evolution of indefinite pronouns and modifiers it followed medieval French syntax, allowing the indefinite aucun
(“some”) to replace the polarity indefinite nul first in non-assertive and then in negative clauses. Administrative prose documents from England and Northern France attest these developments between 1250–1425, with a slight lag in the insular context consistent with
a wave model of the spread of change. The direction of change, in which a positive indefinite spread to other contexts, was unrelated to the patterns of indefinite expressions in Middle English, supporting the view that later Anglo-Norman was largely grammatically independent, not a learner
variety heavily influenced by an English substrate.