Use of "-en" suffix

Solution 1:

You're quite right.

-en as a suffix is of Saxon/German origin.
Made of. In German it is may be a bit oldish but still possible to encounter "wollen" as made of wool ("aus Wolle gemacht"), and quite common to hear "golden" (von Gold gemacht). That's for adjectives.
Plural. For noon, you would have *-en" as a Saxon plural oxen (German Ochsen) or children (Kindern, old-german and dutch Kinderen), bretheren (German: "Brudern", old G. "Bruderen").
In dialectal english you can still find "Hosen" (German "Hosen" => kind of trousers), "Shoon" (G: Shuen), "Housen" (Häusen), "Treen".
Diminutive. Vixen also (German Füchsin : little female of the Fuchs/Fox) is of Saxon origin but this time the "-en" is not the mark of plural.

en- as a prefix this time, is of Latin origin (via French). in- would be directly Latin (sometimes both forms survive : enquiry-inquiry, incase-encase). Strangely enough it also conveys a meaning of "make" as in "turn into" : enslave, enlarge (élargir) enrich (enrichir), enable, endear, endanger.
Some other en- prefixes can be traced back to Greek, enthusiasm, endemic, energy.

However, I don't think there has been a lot of inbreeding between latin "en-" prefix and words of saxon origin. And surely no (legitimate) -en suffix to non saxon words. VAX (meaning Virtual Address eXtension because it was an evolution from 16bits VA space to 32bits VA space) can probably not apply to a Saxon origin ;-).

Many sources: Oxford Dictionary of English Etymology - 1966 Ed.

Solution 2:

The suffix -en is used to form adjectives from nouns (earthen, woolen, golden), but also verbs from adjectives or nouns (widen, deepen, loosen, strengthen, embolden, enliven).
The prefix is also used to form feminine nouns like vixen, which has origin from the Middle English word fixen.

Solution 3:

There is only one truly modern word I know that uses the -en ending: Embiggen.

Of course this word was made up for the TV show 'The Simpsons', where the motto of the town is: "A noble spirit embiggens the smallest man." In the show, a newcomer to the town scoffs at the word and the stupidity of the town's natives, but is rebuked with the response, "It's a perfectly cromulent word."

It is notable for its consistent implementation of the -en suffix.

In the '70s and '80s, it was quite common for computer people to use the -en suffix to pluralize computer nouns, such as VAX or box. These would simply become VAXen or boxen, respectively. This practice borrowed the Germanic -en suffix to denote plurals.