The Collaborative International Dictionary of English v.0.48:

-en \-en\
   1. A suffix from AS. -an, formerly used to form the plural of
      many nouns, as in ashen, eyen, oxen, all obs. except oxen.
      In some cases, such as children and brethren, it has been
      added to older plural forms.
      [1913 Webster]

   2. A suffix corresponding to AS. -en and -on, formerly used
      to form the plural of verbs, as in housen, escapen.
      [1913 Webster]

   3. A suffix signifying to make, to cause, used to form verbs
      from nouns and adjectives; as in strengthen, quicken,
      frighten. This must not be confused with -en corresponding
      in Old English to the AS. infinitive ending -an.
      [1913 Webster]

   4. [AS. -en; akin to Goth. -eins, L. -inus, Gr. ?.] An
      adjectival suffix, meaning made of; as in golden, leaden,
      wooden.
      [1913 Webster]

   5. [AS. -en; akin to Skr. -na.] The termination of the past
      participle of many strong verbs; as, in broken, gotten,
      trodden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

En \En\, n. (Print.)
   Half an em, that is, half of the unit of space in measuring
   printed matter. See Em.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

En- \En-\
   1. [F. en-, L. in.] A prefix signifying in or into, used in
      many English words, chiefly those borrowed from the
      French. Some English words are written indifferently with
      en-or in-. For ease of pronunciation it is commonly
      changed to em-before p, b, and m, as in employ, embody,
      emmew. It is sometimes used to give a causal force, as in
      enable, enfeeble, to cause to be, or to make, able, or
      feeble; and sometimes merely gives an intensive force, as
      in enchasten. See In-.
      [1913 Webster]

   2. A prefix from Gr. ? in, meaning in; as, encephalon,
      entomology. See In-.
      [1913 Webster]

WordNet (r) 3.0 (2006):

en
    n 1: half the width of an em [syn: en, nut]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

EN
       Europa Norm (Europe)