What was the significance of putting salt in a baby's mouth at RC christenings?

I was brought up as RC. This was still the custom when my youngest sibling was baptized [1970]. But I noticed it was not done at an RC ceremony I went to in the late 80s. Can any Catholics tell me what the salt represented?
Update: RE - Perhaps it varies in different countries. Amongst the Catholics I have known, the terms baptism and christening were used.
Update 2: RE - The Catholics I know use both terms. I think ' christen' means 'to make [someone] a Christian, as well as 'to name.'
Update 3: David - I know of Christians of different denominations who say it is good luck if the baby cries, as it means the devil has been driven out. The salt would be likely to make them cry!
Update 4: Using salt to sterilize holy water makes sense.
I was 4 days old when baptized. My mother says when the priest put his finger in my mouth, to give me the salt, I just kept sucking his finger. Well - How was I to know? Sucking is instinctive for babies!
5 answers 5