ên

Neologism based on the word for "centre". Navel is a very conservative word. The best metaphor I could find is for "centre". Ancient Greek "ὀμφαλός" (omphalós), Arabic "سُرّة" (surrah), Japanese "へそ" (heso) and Sanskrit "नाभि" (nābhi) all seem to imply "centre". Other sources from PIE, Russian, Chinese, Hebrew, etc, seem to all have a native word for navel. So I've picked the root for "centre" and simply applied the phonetic rules, ending up with "ên".