epenthesis

noun, plural ep·en·the·ses [uh–pen-thuh-seez] /əˈpɛn θəˌsiz/.

1. the insertion of one or more sounds in the middle of a word, as the schwa in the nonstandard pronunciation [el–uh m] /ˈɛl əm/ of elm.

noun plural -ses (-ˌsiːz)

1. the insertion of a sound or letter into a word