index case
n.— «A man whom doctors call the “index case”—the first patient they knew about—got sick in December 2006 and was hospitalized at the Mayo Clinic for about two weeks.» —“A Medical Mystery Unfolds in Minnesota” by Denise Grady in Austin, Minnesota New York Times Feb. 5, 2008. (source: Double-Tongued Dictionary)
Further reading
Brian from Lafayette, Indiana, wonders why chicken is abbreviated CHX in the restaurant industry. Using X as a substitute or shortener has a long history. Medieval scribes sometimes drew a line through the final stroke of an abbreviated word. This...
In 1916, a small-town newspaper in Pennsylvania printed a fanciful item about a local gathering with a guest list that included, among others, Miss Ella Vader, Mr. Ray Zor, and other punny names. This is part of a complete episode. Transcript of...