a mugger is someone who robs; aka a robber.
Mugger:
1. One who commits a
mugging.
2. One who makes exaggerated faces, as in performing.
3. A large crocodile (Crocodilus palustris) of southwest Asia,
having a very broad wrinkled snout.
someone who studies hard isn't called a mugger, and the term 'mug'
means rob.
Mug:
noun 1. a drinking cup, usually cylindrical in shape, having a
handle, and often of a heavy substance, as earthenware.
2. the quantity it holds.
3. Slang. a. the face.
b. the mouth.
c. an exaggerated facial expression; grimace, as in acting.
d. a thug, ruffian, or other criminal.
4. British Slang. a gullible person; dupe; fool.
verb (used with object)
5. to assault or menace, esp. with the
intention of robbery.
6. Slang. to photograph (a person), esp. in compliance with an
official or legal requirement.
verb (used without object) 7. Slang. to grimace; exaggerate a
facial expression, as in acting.
the term 'mugged up' means hit the books or to study.
can't believe we've got secondary to uni students using the wrong
term when it comes to examination period. disgraceful.
check your english.
oh. fyi, i hope this helps - www.dictionary.com
and to that b*stard in your class, you can simply ignore him. So
what if people don't know your name. That means he didn't think
much of you or of any significance as a friend or something. Lay
back and take a chill pill. 
