A follower of the philosopher Diogenes was called this, from the Greek for "doglike"
[DOC] [TLE] Cynic | Define Cynic at Dictionary.com [PAR] (initial capital letter) one of a sect of Greek philosophers, 4th century b.c., ... 1540-
50; < Latin Cynicus < Greek Kyniks Cynic, literally, doglike, currish, ... You, dear 
reader and refusenik, will likely be called a cynic or a sad sack by friends.