This website quotes Joseph Tabory as saying that the earliest known appearance of Pour Out Your Wrath in a Haggada was in the Machzor Vitry (p. 296) which dates back to around 1200 (See https://www.sefaria.org/sheets/105867?lang=bi)
Two horrific events/periods (that I mention below) occurred not before or long after that. I presume there was a lag between the time Pour Out Your Wrath was first put in the Haggada and the time it was widespread. My question is, when did it become widespread.
There was considerable violence against Jews in the 1300's around the time of the Black Death when some 40% of the population of Europe died. Was the inclusion of "Pour out your wrath" linked to the Bubonic Plague and the contemporaneous extermination, by burning, of most of the Jews in Germany, or did its inclusion become more prevalent then? (See, for example, https://pubmed.ncbi.nlm.nih.gov/11625662/)
Or was it linked to the First Crusade in the 1000's when the crusaders looted and massacred Jews on their way to liberate Jerusalem from the Moslems. (See, for example, https://www.myjewishlearning.com/article/the-crusades/)
