chained_bear commented on the word mackerel-snapper I get the fish-eater thing, but I don't know why non-Catholics wouldn't want mackerel--evidenced by the use of the term in a disparaging phrase. (Or wouldn't want snapper, for that matter.)
Psalm 1 is the first of the Psalms in the Hebrew Bible. Like many of the psalms, it contrasts the  righteous  person (tzadik ×¦×××§) to the wicked or ungodly (rasha` ×¨×©×¢) or the  sinner  (chatta' ×××).
Doubtless Davidâs psalms did much to inspire later servants of God to use this method of expression. The first forty-one psalms were all written by David, and it is believed that he compiled these into a book, which later was used in the temple services. Eventually the whole Book of Psalms was thus used.