Look, it's true that Latin nouns (a noun is a word which describes an object, like a table or a law or an idiot) behave oddly (to an English speaker) when they arrive in groups.
Servus = servant; servi = more than one servant.
Obviously it would be much easier if the Roman's had made the more-than-one-servant word servuses, but they didn't. It was probably something to do with the fact that the Romans were completely ignorant of the grammar of the English language - and that was probably because when they were around the English language hadn't actually been invented, yet.
Now, people naturally like to show off their knowledge, and so if a word looks like a Latin noun they will often give it a Latin-like ending if the thing suddenly pops up in a group.
But just because a word looks like a Latin noun, it doesn't mean that it is one.
Ignoramus, for instance, is not a Latin noun.
And the people who use the form ignorami are actually ignoramuses.
Word To Use Today: ignoramuses. This word is legal Latin for we have no knowledge of, from the Latin ignōrāre, to be ignorant of. It's use in English began with the character of an ignorant lawyer in George Ruggle's 1615 smash-hit play Ignoramus.
If only the play had had two ignoramuses!