Why do we have middle names?

[Houseplantmad]

just wondering why we do - when they don’t usually ever get used. Why bother with them when some people get themselves so stressed choosing just a first name?

My Nan was Catholic and so all of my mums side has two middle names and so do me and my siblings and now my two (family tradition) I never questioned it but apparently it's in case you convert to be a priest or nun and so you choose your middle name to be your religious name (or something like that) but don't hold me to that!

I think it's to reduce the likelihood of someone else having the same name as you.