The term 'Thanksgiving Song' can be broken down into two crossword solutions: PAEAN (5 letters) and PSALM (5 letters). A PAEAN is a song or poem of praise, often used to honor a deity or hero. It is derived from the Greek word 'paian' which means 'song of triumph'. A PSALM is a sacred song or poem, usually from the Bible, that is used in religious worship. It is derived from the Greek word 'psalmos' which means 'HYMN'. Both paeans and psalms are used to express gratitude and praise, making them appropriate for a Thanksgiving song.