The term 'SOURCE OF STRENGTH' can be represented by the crossword solutions SINEWS (6 letters), UNITY (5 letters), SINEW (5 letters), FORTE (5 letters), ASSET (5 letters), UNION (5 letters), and NEWEST (6 letters). SINEWS refers to the tendons and muscles that give strength to the body, while UNITY and UNION refer to the strength of a group or collective. SINEW is a synonym for SINEWS, and FORTE and ASSET both refer to something that is strong or advantageous. Finally, NEWEST implies that the source of strength is something that is new or recently discovered.