12-Letter Words Matching _N________M_

There are 13 12-letter words that match _N________M_. 2 are common words, such as ANACHRONISMS and INTERREGNUMS. A rarer one is ANTIREALISMS. In this set, I is the most frequent open letter (13 words). 3 words contain a doubled letter.

Full list 13

anachronismsinterregnumsantheridiumsantirrhinumsendocardiumsendometriumsendotheliomainfantilismsunnilhexiumsantependiumsantielitismsantifascismsantirealisms

About this list

Words
13 (2 common words)
Common example
anachronisms
Rare example
antirealisms
Doubled letters
3
Ending in S
12
Most frequent letter
I (13)

Questions

How many 12-letter words matching _n________m_ are there?

13. 2 of them are common words.

What is a common example?

ANACHRONISMS is among the common words in this set.