A hypocorism is a pet name or diminutive. For example, Bob, Rob, Bobby, Robbie (from Robert). I came across this word for the first time the other day and had to look it up because I didn’t know what it meant.
Hypocorisms or diminutives seem to be more widely used in some languages than in others. The Slavic languages use them a lot, and not just for people’s names – just about any noun has a hypocoristic form. At least that’s what my Czech, Slovak, Polish and Russian-speaking friends tell me.
Hypocoristic affixes in English include
-ey/y/ie, as in doggie (dog), horsey (horse), barbie (barbeque), postie (postman/woman), tinnie (tin [of beer]), cozzie (swimming costume), mozzie (mosquito), footie/footy (football). This affix is particularly popular in Australia and Scotland.
-ling, as in duckling, gosling
-ette, as in kitchenette, cigarette, towellette
-let, as in piglet
Can you think of any others?
There are more examples of hypocorisms/diminutives in a variety of languages here.