It seems that the "ss" sequence is treated abnormally by the auto completition engine.
I noticed the issue typing "oss" and having the following suggestions:
macosx (194)
centos (141)
osx (122)
hosting (119)
postfinx (77)
web-hosting (65)
That is not what one expects of course
writing an additional "s" seems to make "osss" be treated as wanted ("oss") by the engine, resulting in the following, good, suggestions:
moss (32)
jboss (16)
cross-platform (7)
moss-2007 (5)
data-loss (3)
jboss-cache (1)