The very particular voice that Manolo Solo uses to play his character was developed as a joke in rehearsals, but director Raúl Arévalo liked it so much that ask him to use it in the movie.
The project took eight years to get made because co-writer/director Raúl Arévalo wanted an specific cast, to shoot in 16mm, which was more expensive and didn't want to change aspects of the story to make it more mainstream. It wasn't until producer Beatriz Bodegas worked with Arévalo in La vida inesperada (2013) that the film started to be produced.
Producer Beatriz Bodegas took a mortgage on her own house to pay for the movie.
The original title of the movie, "tarde para la ira" ("slow to anger"), is a reference to Exodus 34:5-7: "The LORD, the LORD, the compassionate and gracious God, slow to anger, abounding in love and faithfulness, maintaining love to thousands, and forgiving wickedness, rebellion and sin. Yet he does not leave the guilty unpunished; he punishes the children and their children for the sin of the parents to the third and fourth generation."
The English title for the movie, "The Fury of a Patient Man" is a direct reference to a quotation from Publilius Syrus, a Latin writer of maxims in the 1st century BC. In the 17th century, more commonly known because British poet and dramatist John Dryden used it in "Absalom and Achitophel" (1681), generally considered to be the greatest political poem in the English language. Similarly to the movie's theme the quote implies that the anger of people who are normally slow to anger is, when it eventually comes, terrible.