During the infamous pogroms of Ta”ch V’Ta”t (years 5408 and 5409 – 1648-1649) the Tosafos Yom Tov fasted and beseeched that from on High it be revealed to him why such terrible calamities had befallen the Jewish people. It was revealed to him from on High that there was lightheaded, idle chatter in shul. People spoke in shul and in the middle of davening, which caused a blemish in the letter “vav” and the word for speech, dibur, was transformed into dever, a plague! When he learned of this, he composed a special prayer (others say the Maharal composed it but the Tosafos Yom Tov instituted and enacted its recitation in his kehillos. See the original nusach below) to help increase the awareness of the power of silence in shul, the destructive nature of idle chatter, and talking in shul and during davening. It is printed in many siddurim alongside the Mi Sheberach we recite on Shabbos after the reading of the Torah.
