Definify.com
Webster 1913 Edition
Apron string
A′pron stringˊ
.The string of an apron. 
To be tied to a wife’s apron strings 
or To be tied to a mother's apron strings
to be unduly controlled by a wife or mother.
 He was so made that he could not submit 
to be tied to the apron strings 
even of the best of wives. Macaulay.