[arundelo]

“[A]lmost anything ending in ‘x’ may form plurals in ‘-xen’ (see VAXen and boxen in the main text). Even words ending in phonetic /k/ alone are sometimes treated this way; e.g., ‘soxen’ for a bunch of socks. Other funny plurals are the Hebrew-style ‘frobbotzim’ for the plural of ‘frobbozz’ (see frobnitz) and ‘Unices’ and ‘Twenices’ (rather than ‘Unixes’ and ‘Twenexes’; see Unix, TWENEX in main text). [...] The pattern here [...] is generalization of an inflectional rule that in English is either an import or a fossil (such as the Hebrew plural ending ‘-im’, or the Anglo-Saxon plural suffix ‘-en’) to cases where it isn't normally considered to apply. This [...] is grammatical creativity, a form of playfulness.”

http://catb.org/jargon/html/overgeneralization.html