-athon
a suffix extracted from marathon, occurring as the final element in compounds which have the general sense “an event, as a sale or contest, drawn out to unusual length, often until a prearranged goal, as the contribution of a certain amount of money, is reached”: walkathon; readathon.
Also
-a-thon,
-thon.
British Dictionary definitions for -thon
-thon
suffix forming nouns
indicating a large-scale event or operation of a specified kind
telethon
Word Origin for -thon
C20: on the pattern of
marathon