The Spanish head of government has, since 1938, been known in Spanish as the Presidente del Gobierno – literally President of the Government, but the term 'president' is far older. Spain was not unique in this regard: it was one of several European parliamentary systems including France, Italy and Ireland that styled the head of government as 'Presidents' of the government rather than the Westminster term of 'Prime Minister' (see President of the Council for the full list of corresponding terms); similarly, the President of the Congress or Senate referred to the parliamentary speakers. This system of multiple distinct offices all labelled 'president' causes confusion among English-speakers: both President George W. Bush and his brother, Florida Governor Jeb Bush, referred to José María Aznar as "President" on separate occasions, and Donald Trump referred to Mariano Rajoy both as "President" and "Mr. President" during Rajoy's 2017 White House visit. While this term of address was not incorrect, it could be culturally misleading to or for English-speakers, so that "Prime Minister" is often used as an inexact but culturally equivalent term to ensure clarity.
The custom to name the head of government as "President" dates back to the reign of Isabella II of Spain, specifically to 1834 and the regency of Maria Christina of the Two Sicilies when, styled after the head of government of the French July Monarchy (1830), the official title was the Presidente del Consejo de Ministros ("President of the Council of Ministers"). This remained until 1939, when the Second Spanish Republic ended. Before 1834 the figure was known as Secretario de Estado ("Secretary of State"), a denomination used today for junior ministers.