There’s a motorcycle part called the “enrichener.” To my ears, it sounds like the “en-” prefix and “-en” suffix (in the enrichen part of enrichener) are redundant.
Of course, there is also “enlighten” which follows the same “en- -en” pattern (and, before someone else mentions it, The Simpsons’ contribution to redundancy, “embiggen,” is closely related).
What, exactly, is going on with words formed with this kind of “circumfix?”
Best Answer
Michael Quinion, Ologies and Isms: Word Beginnings and Endings (2003) says that the prefix en- for forming verbs and the suffix -en for forming verbs come from very different sources:
[Note: Throughout the preceding extract, I have removed the author's numerous example words; to see them, you'll have to buy the book.]
A word like enrichen thus exhibits not only mixed parentage but an excess of verb-forming attachments. In general (and in the absence of guidance from The Simpsons) it's probably a good idea in forming new verbs to commit either to embig or to biggen, but not to embiggen.
UPDATE (9/26/14): In looking over this answer, I noticed a link in the LINKED column of the page to an earlier question, Verb form of "to blacken" versus "to brown". In his answer to that question, John Lawler points out several words that, like enrichen, have paired en-/em- prefixes and -en suffixes: embolden, enhearten, enlighten, and enliven. Readers intrigued by the question about en- and -en asked here will probably find that answer interesting, too.