Emily Dickinson Lexicon

IM, adv.

In composition, is usually the representative of the Latin in; n being changed to m, for the sako of easy utterance, before a labial, as in imbibe, immense, impartial. We use the same prefix in compounds not of Latin origin, as in imbank, imbitter. For im, the French write em, which we also use in words borrowed from their language.