Hypocorism

A hypocorism ( hy-POK-ər-iz-əm or HY-pə-KORR-iz-əm; from Ancient Greek ὑποκόρισμα hypokórisma; sometimes also hypocoristic), or pet name, is a name used to show affection for a person. It may be a diminutive form of a person's name, such as Izzy for Isabel or Bob for Robert, or it may be unrelated.