-itis

1.
a suffix used in pathological terms that denote inflammation of an organ (bronchitis; gastritis; neuritis) and hence, in extended senses, nouns denoting abnormal states or conditions, excesses, tendencies, obsessions, etc. (telephonitis; baseballitis).
Origin
< Neo-Latin (or Latin) -ītis < Greek
British Dictionary definitions for -itis

-itis

suffix
1.
indicating inflammation of a specified part: tonsillitis
2.
(informal) indicating a preoccupation with or imaginary condition of illness caused by: computeritis, telephonitis
Word Origin
New Latin, from Greek, feminine of -itēs belonging to; see -ite1
Word Origin and History for -itis

noun suffix denoting diseases characterized by inflammation, Modern Latin, from Greek -itis, feminine of adjectival suffix -ites "pertaining to." Feminine because it was used with feminine noun nosos "disease," especially in Greek arthritis (nosos) "(disease) of the joints," which was one of the earliest borrowings into English and from which the suffix was abstracted in other uses.

-itis in Medicine

-itis suff.
Inflammation or disease of: laryngitis.

-itis in Science
-itis  
A suffix meaning "inflammation," as in bronchitis, inflammation of the bronchial tubes.
Slang definitions & phrases for -itis

-itis

suffix

used to form nouns An excessive and probably unhealthy involvement with or prevalence of what is indicated: committeeitis/ symbolitis (1903+)