The term 'It's a Mystery' can be represented by four different crossword solutions: ENIGMA (6 letters), Closedbook (10 letters), Nooneknows (10 letters), and Heavenonlyknows (15 letters). ENIGMA is a word of Greek origin meaning 'RIDDLE' or 'PUZZLE'. A closedbook is something that is not open to discussion or investigation. Nooneknows is a phrase used to express the idea that something is unknown or unknowable. Heavenonlyknows is an expression used to suggest that only God knows the answer to a particular question. Together, these four crossword solutions represent the idea that something is mysterious and unknowable.