To hearten someone is to make them feel happier and more hopeful. Good news heartens you. A kind message can hearten a tired team. The heart here is courage and hope, not the organ, and not romantic love. The verb is a little old-fashioned and a little formal; many people today would say cheer up, encourage, or lift someone's spirits. You still meet it in news and books: The result will hearten supporters. The adjective heartening is common: heartening news. Though actually, hearten is what one person or one piece of news does to another; take heart is what you do yourself, and lose heart is the opposite movement. It does not mean to give someone a heart, and it does not mean to make them fall in love.