If I remember well, in the Bible there is Benjamin, who was born when his father was old enough; he was just a baby when the other children were already grown, so he was the one the father preferred.
It is used to say "the child most loved".

You remember very well, emanuela. Jacob's affection for Benjamin was laso connected with Benjamin's being the son of his favourite wife, Rachel, who died giving birth to him - a connection with CapK's explanation of the term.