Within most medieval books of hours, there were ecclesiastical calendars that had important holy days printed in red. This was a type of textual highlighting used to call attention to important festivals; a visual language that had long indicated significant textual features, paragraph organization, and wordplay (e.g. acrostics). The Latin word for red ochre and red coloring in general was rubrīca. As such, making a text red is called “rubrication” and influenced the original use for the word “rubric.” The practice of coloring significant dates in red is perhaps best known through the English idiom of a “red letter day.”