In addition to their obvious physical discomfort, thorns represented the curse of sin to Jews. Genesis records that the first two people, Adam and his wife Eve, committed the first sin by deliberately disobeying God. Consequently, God banished them from their home and cursed them. Part of this curse was against the earth itself, which became less fruitful and required strenuous labor to produce food. Additionally, thorns began growing along the ground to further afflict them. 

The ground is cursed because of you. You’ll eat from it in pain all the days of your life. Thorns and weeds will grow for you and you’ll eat plants from the field. You’ll eat bread by the sweat of your face until you return to the ground, because you were taken from it. You are dust and you’ll return to the dust.

 – Genesis 3:17-19