Thesaurusi (or how descriptivist can you go?)

Over the past month or so there has been an influx of new editors at the Simple English Wiktionary (and you're more than welcome to join us). One of them saw fit to add an entry for thesaurusi, after all, there was one on the English Wiktionary. I headed over there and sure enough, there it was.

You see how it got there don't you? If you look up thesaurus in a dictionary, it tells you that there are two possible plurals +es or +i. Now if you've never noticed that some English nouns that end in -us form their plurals by dropping the -us and replacing it with -i, it would make sense just to stick an -i on the end and voila!

I referred the obvious mistake for deletion, but lo and behold, thesaurusi is actually out there, and not just in the nescient scribblings of some teenage facebook adict.

• 1965, Pierre A. Rinfret, “Changing Population and Changing Demand”, Financial Analysts Journal, Vol. 17 No. 5, page 75: 

  In the closing weeks of 1959 and the early weeks of 1960, book dealers must have had a bonanza in selling thesaurusi.

• 1999, Lynn Tooma et al., Exploring the Bible, ISBN 0884894649, page 49:

  Gather a variety of dictionaries and thesaurusi written for middle-school students as well as adults.

• 2004, Vincent Mary, “MeSH and Specialized Terminologies”, in MedInfo 2004, ISBN 1586034448, page 530:

  UMLS is an integration of several thesaurusi.

A discussion ensued and it was decided to keep it with the following entry:

"(rare, considered nonstandard) Misconstruction of thesauruses, plural form of thesaurus."

At the SEWikt, we've put a redirect to thesauri and left it at that. But don't be surprised if one dark night, just when you least expect it, you stumble across alumnusi, stimulusi, fungusi, nucleusi, cactusi or one of their ilk and you find yourself running screaming down the street, your descriptivist sensibilities flapping behind you in tatters.