The titular designation "Member of Provincial Parliament" and the acronym "MPP" were formally adopted by the Ontario legislature on April 7, 1938.
Prior to Confederation in 1867, members of the Legislative Assembly of the Province of Canada had been known by various titles, including MPP, MLA and MHA.
As an alternative, a resolution was adopted fixing the title as Member of Provincial Parliament (MPP).
[1] 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.
Members of other Canadian provincial and territorial assemblies employ the titles: