A sop is a piece of bread

Bread

Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...

 or toast

Toast

Toast is bread that has been browned by exposure to radiant heat. This browning reaction is known as the Maillard reaction. Toasting warms the bread and makes it firmer, so it holds toppings more securely...

 that is soaked in liquid food and then eaten. In medieval cuisine

Medieval cuisine

Medieval cuisine includes the foods, eating habits, and cooking methods of various European cultures during the Middle Ages, a period roughly dating from the 5th to the 16th century...

, sops were very common. Sops were served with wine

Wine

Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

, soup

Soup

Soup is a generally warm food that is made by combining ingredients such as meat and vegetables with stock, juice, water, or another liquid. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth.Traditionally,...

 or broth

Broth

Broth is a liquid food preparation, typically consisting of either water or an already flavored stock, in which bones, meat, fish, cereal grains, or vegetables have been simmered. Broth is used as a basis for other edible liquids such as soup, gravy, or sauce. It can be eaten alone or with garnish...

, 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

Soup

Soup is a generally warm food that is made by combining ingredients such as meat and vegetables with stock, juice, water, or another liquid. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth.Traditionally,...

" is a cognate

Cognate

In linguistics, cognates are words that have a common etymological origin. This learned term derives from the Latin cognatus . Cognates within the same language are called doublets. Strictly speaking, loanwords from another language are usually not meant by the term, e.g...

 of "sop", both stemming ultimately from the same Germanic

Germanic languages

The Germanic languages constitute a sub-branch of the Indo-European language family. The common ancestor of all of the languages in this branch is called Proto-Germanic , which was spoken in approximately the mid-1st millennium BC in Iron Age northern Europe...

source.

The word is mentioned prominently in the Bible, King James Version:

When Jesus had thus said, he was troubled in spirit, and testified, and said, Verily, verily, I say unto you, that one of you shall betray me. Then the disciples looked one on another, doubting of whom he spake. Now there was leaning on Jesus' bosom one of his disciples, whom Jesus loved. Simon Peter therefore beckoned to him, that he should ask who it should be of whom he spake. He then lying on Jesus' breast saith unto him, Lord, who is it? Jesus answered, He it is, to whom I shall give a SOP, when I have dipped it. And when he had dipped the SOP, he gave it to Judas Iscariot, the son of Simon. ( John 13:21-26 )

Expressions

The expression "milksop" describes a person as weak and indecisive, as in "you milksop," meaning "you wimp".