Webster1913 would like you to know that emeritus comes from the Latin emerere, which is e + merere, out + serve = basically, to complete one's term of service; to merit; to earn.
thanks to:
http://www.adelaide.edu.au/HR/policies/typeappt/emerprof.htm
http://www.cqu.edu.au/documents/unipol/professor_emeritus.htm
http://www.usask.ca/vpacademic/policies/professor_emeritus.html
Webster1913