2、em, 来自PIE*ai, 燃烧，词源同ash, edifice. -b, 插入字母。-er, 来自拉丁文uro, 燃烧，词源同combust.
2、ember: [OE] Ember goes back to a prehistoric Germanic *aimuzjōn, although it is possible that the modern English word represents a borrowing from the related Old Norse eimyrja rather than a direct line of descent from Old English ǣmyrge. The ember of Ember days , incidentally, ‘days following certain Christian festivals’, is a completely different word. It comes from Old English ymbryne ‘circuit’, literally ‘running round’, a compound formed from ymb ‘round’ and ryne ‘course, running’, a relative of modern English run. It was applied to these particular days of the Christian calendar because they ‘come round’ four times a year.
4、"small, live coal," Old English æmerge "ember," merged with or influenced by Old Norse eimyrja, both from Proto-Germanic *aim-uzjon- "ashes" (cognates: Middle Low German emere, Old High German eimuria, German Ammern); a compound from *aima- "ashes" (from PIE root *ai- (2) "to burn;" see edifice) + *uzjo- "to burn" (from PIE root *eus- "to burn;" source also of Latin urere "to burn, singe"). The -b- is intrusive.