-y2 [in nouns]
1 also -ieXX
used to make a word or name less formal, and often to show that you care about them - used especially when talking to children:
Where's little Johnny?
my daddy (=my father)
What a nice doggy (=dog)!
used to make nouns from some verbs to show an action:
the expiry date (=the date when something expires)
an inquiry (=the act of inquiring about something)