The name "Old 100th" derives from the use of this hymn for Psalm 100 (All People That on Earth do Dwell) though the tune has also been used with Psalm 134. The first known publication of the music is in the 2nd edition of the Genevan Psalter, a hymn book compiled in 1551 by the French composer Loys (or Louis) Bourgeois in the Swiss city of Geneva. Although it is not certain, the music is assumed to have been composed by Bourgeois (1510-1560) himself. The "Old 100th" therefore has a long history and has been used by many Christian churches throughout Europe and elsewhere. The tune has been used also by other composers including Bach in the final movement of his cantata "Herr Gott, dich loben alle wir", Mendelssohn in the 4th movement of his Piano Trio in C minor Op 66, and also by Ralph Vaughan Williams in his arrangement of "The Hundredth Psalm". More hymns can be found in our article about Church Music.
Here is a video of Old 100th for piano:
The image below is the first page of the sheet music, and here you can download the full sheet music for Old 100th for piano in PDF format.