A sop is a piece of bread or toast that is soaked in liquid food and then eaten. In medieval cuisine, sops were very common. Sops were served with wine, soup or broth, and then picked apart into smaller pieces to soak in the liquid. At elaborate feasts, bread was often pre-cut into finger-sized pieces rather than broken off by the diners themselves. The word "soup" is a cognate of "sop", both stemming ultimately from the same Germanic source.
Some people also use the expression 'you milk sop' meaning you wimp.
Adamson, Melitta Weiss (2004) Food in Medieval Times ISBN 0-313-32147-7