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.