The phrasing that I hear more often is "make illegal states unrepresentable"; both the submitted article and Alexis King's original article use this phrase. At least according to https://fsharpforfunandprofit.com/posts/designing-with-types..., it originates from Yaron Minsky (a programmer at Jane Street who is prominent in the OCaml community).
EDIT: Parent comment was edited to amend the "impossible/unrepresentable" wording
EDIT: Parent comment was edited to amend the "impossible/unrepresentable" wording