Linguistics Club
Linguistics Club
[Megan talks to Ponytail.] Megan: You should come to our Linguistics Club's sesquiannual meeting. Megan: Membership is open to anyone who can figure out how often we meet.

A " sesquiannual " meeting is one that occurs one and a half times every year; equivalently, 3 times every 2 years, or once every 8 months (this could be taken even more literally by having one meeting during each year, and another meeting which spans midnight every other New Year's Eve, thus having a one and a half meetings each year).
The term comes from the Latin prefix " sesqui- ", which means "one and a half", and the root word " annual ", which equates to "…times per one year". The root word "annual" is commonly confused with the suffix " -ennial ", meaning "one time per x years." In particular, “sesquiannual” should not be confused with “ sesquiennial ”, meaning "one time per one and a half years" or every one and a half years (18 months). Note that the Wiktionary entry on sesquiannual has both meanings listed – both 8 month and 18 months intervals. This is an extension of the common confusion between "biannual," meaning "twice a year", and "biennial", meaning "once every two years". Compare with the Sesquicentennial Exposition celebrating the first 1½ centuries of the United States, and "sesqui bi centennial", being 'half and two' hundred years, i.e. 250 (even though it should properly be sestercentennial, based on the Latin sestertius , meaning "(two and) half of a third").
The joke suggests that only a competent linguist could understand the word “sesquiannual”. One reason for this is that the prefix “sesqui-” is rare, so those who know its meaning are likely to be linguists. Another is that a competent linguist should be able to distinguish between “sesquiannual” and “sesquiennial”.
If you understand this then you can join the Linguistics Club . While most organizations attempt to ensure that the schedule of their meetings are clear to participants so that everyone will attend, the club in the comic deliberately instills an ambiguity for those outside their target demographic. Their membership will thus swell with the desired cognoscenti who remain unconfused, and maybe also a few lucky guessers.
Once the applicant correctly understands the frequency of meetings, presumably they are told at least one meeting date in the cycle so that an attendance can be made.
Regarding the title text, a tautology is a statement that is true (or self-evident) because of its logical form, such as "all birds are birds" or "A = A." As such, the statement "the Tautology Club meets on the date of the Tautology Club's meeting" is itself tautological.
While the membership requirement for the Linguistics Club is merely to know the intended frequency, the Tautology Club's stipulation appears to require an eligible member to derive a valid meeting date from thin air without any clue at all (and no indication that there is even a regular cycle of any kind). This would definitely be more of a challenge.
The title text has a connection to 703: Honor Societies in which Cueball creates a Tautology Club where tautologies are used in practically every spoken sentence.
[Megan talks to Ponytail.] Megan: You should come to our Linguistics Club's sesquiannual meeting. Megan: Membership is open to anyone who can figure out how often we meet.
