A penchant is a strong preference or tendency. If you have a penchant for pizza, you either eat it daily or wish you did.
Penchant borrows from French, in which penchant literally means inclined. It goes back to the Latin pendere, for hanging, which is also the source of pendant. In both French and English, speakers have long used the idea of inclination metaphorically: a hillside can be inclined in one direction or another, and so can a person's thoughts. But in English, penchant is only for desires.