Why is the 23rd Psalm named thusly?

Answer 1

Because it comes from The Bible - the Book of Psalms in the Old testament, and this particular psalm is number 23 out of the 150 psalms listed there. In the Bible there are just 150 psalms, although there are others too (the so-called psalm 151, 152 etc) but these were not included in the Old Testament. The psalms were listed in various ways, groups of psalms written by King David, others by Solomon, his son, and others by unknown writers. Some were grouped as praise psalms, some as psalms of penitence and so on. Psalm 23 was written by King David as a devotional psalm likening God to a shepherd - something with which David was familiar as he was himself a shepherd when he was a young boy.