"retard" means "slow" in languages other than English. It is in reference to the ester.
re·tard 1 (r-tärd)
v. re·tard·ed, re·tard·ing, re·tards
v.tr.
To cause to move or proceed slowly; delay or impede.
v.intr.
To be delayed.
n.
1. A slowing down of progress; a delay.