The titular designation "Member of Provincial Parliament" and the initialism "MPP" were formally adopted by the Legislature on April 7, 1938. Prior to the adoption of this resolution, members had no fixed designation. Prior to Confederation members of the Legislative Assembly of the Province of Canada had been known by various titles including MPP, MLA and MHA and this confusion persisted after 1867 with members of the Ontario legislature using the titles Members of the Legislative Assembly (MLAs) or Members of Provincial Parliament (MPPs) interchangeably.
In 1938, Frederick Fraser Hunter, the Member for St. Patrick, introduced a private member's bill to designate members as Members of Parliament (MPs) arguing that the titles of MPP or MLA were confusing, inaccurate, and undignified. However, his original proposal failed to pass and as an alternative a resolution was adopted fixing the title as Members of Provincial Parliament (MPP).
The text of the resolution passed by the House on that day is as follows:
On motion of Mr. Hunter, seconded by Mr. Miller,
Resolved, That in all matters of address, titular distinction, formal correspondence, official proceedings and all similar matters having to do with and coming under the jurisdiction of the Legislature of Ontario, the members of the Legislative Assembly shall be entitled to the designation "Member of Provincial Parliament" and its abbreviation "M.P.P."
Ontario is the only Canadian provincial legislative assembly to employ this designation. Members of other Canadian provincial and territorial assemblies employ the titles:
"MPP" was the titular designation of the members of the Legislative Assembly of Lower Canada from 1791 to 1838.