Half a century is a landmark. Settled, little care for children, got it all in a row... and still young enough to dance and party. A good reason (if needed anyway) to celebrate or to be celebrated.
About men, we then say that they saw Abraham.
And for the ladies: she has seen Sara (h), (the biblical wife of Abra (ha) m).
On your 50th you’re supposed to have about the wisdom of Abraham....

So you'll know where Abraham gets his mustard.
That in turn means: to know what is on sale in the world, know all the fine, being well aware of the case.

A number of other crown years (multiples of 10) is named to Biblical people.

  60: Isaac (or Rebekah)
  70 years: Jacob (or Rachel)
  80 years: Joseph (or Asenath)
  90 years: Ephraim
100 years: Methuselah

Since 1992 (12th edition) says our Dutch dictionary about Sara: "puppet of bread dough, pastry, meat or fabric in the shape of an old woman, that a woman is given on her fiftieth anniversary as a gift."
Abraham also get in different regions a decorated bread or pastry puppet in the form of an (old) man with glasses, pipe, rod, and a beard.