I've been asked to confirm that the correct plural form of "ignoramus" is "ignorami."
Sorry, but no. As with most singular nouns ending in -s, the plural of "ignoramus" is formed by adding -es. So when one ignoramus hooks up with another, you have a couple of ignoramuses.
True, "ignoramus" is a Latin loan word, but it's derived from a verb ("ignorare")--unlike, say, "stimulus," which comes from a noun and is one of the few Latin borrowings to retain the plural ending of -i.
In Modern American Usage (Oxford University Press, 2003), Bryan Garner traces the history of "ignoramus":
Until 1934 in England, if a grand jury considered the evidence of an alleged crime insufficient to prosecute, it would endorse the bill ignoramus, meaning literally "we do not know" or "we know nothing of this." Long before, though, the word ignoramus had come to mean, by extension, "an ignorant person." In 1615 George Ruggle wrote a play called Ignoramus, about a lawyer who knew nothing about the law; this fictional lawyer soon gave his name to all manner of know-nothings, whether lawyers or nonlawyers.
For the record, in the original Latin version of the comedy Ignoramus, George Ruggle did use "ignorami" as a plural noun. But in his 1660 translation, Fernando Parkhurst provided the conventional English plural:
Hush, hush, peace, peace, keep the peace with your hands. You laugh and clappe, but what shall become of your poore Ignoramus? For unless I take out a writ of non molestando, my brother Ignoramuses will trubble mee with noe mercy.
(Epilogue of Ignoramus, by George Ruggle, 1615; translated by Fernando Parkhurst, 1660)
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