To squat = to illegally live in/on or take possesion of a home/house or piece of land.
To squat also has another meaning = to study hard and learn as much information as possible about a subject, before an exam.
To squat up on shakespeare would mean to learn as much about him as possible.
We usually use this phrase before taking an exam, if the exam is near and you have not done your homework.
It is becoming a little outdated
"to cram" means the same also a little outdated.
Or it could be a bad English-Spanish Spanish-English translation.