As Mozart’s works have numbers beginning with “K”, Bach’s works have numbers beginning with “BWV”. These were all given to the individual works by the scholar who made an inventory of their works, and a number to be referred to as a reference number.
Mozart’s “K” stands for “Kechel” and is named after Köchell who has cataloged Mozart’s works, and Bach “BWV” is an abbreviation for “Bach Werke Verzeichnis” and this is Wolfgang Schmieder. The first edition was published in 1950.
At that time, Bach works had been said to have remained 1080 songs, so BWV numbers were also said to have 1080 songs left, so BWV numbers were up to 1080, but then research progressed, and the currently published version Then the BWV number is attached to 1120 songs. Depending on future research, there may be more possibilities.