At Christmastime especially, it is not uncommon to hear Jesus being referred to as Emmanuel. Or wait, is it Immanuel? Christmas cards say it, parishoners and carolers sing it, preachers wax eloquent on it, churches are named after it, but...How is it really spelled?
Well, the question isn't really "How is it "spelled?", the question is "How is it transliterated in English?" Because it is a name, we transliterate. Transliteration is not the same as translation. Whereas translation is a "meaning for meaning" equivalent, transliteration is merely a "letter for letter" equivalent. So, that's what we're going for...a letter for letter equivalent.
There are three verses, then, in the Bible where the name is used. Two of those are in Hebrew (Isa 7.14 and 8.8) and one of them is in Greek (Mt 1.23). In Isaiah, we find a Hebrew compound used: (עִמָּ֥נוּ אֵֽל) ʿimmānû + ʾēl (immanu means "with / together with", while El means "God"). In Greek we have the single word (Ἐμμανουήλ) Emmanouḗl. Notice that in the Hebrew we have the ayin with the subscripted hireq. It is for this reason that we use an "I" when we transliterate the name. In Greek, we have the smooth breathing mark followed by the capital Epsilon, giving us the transliteration that begins with an "E". The LXX (Septuagint) transliterates the Hebrew this way also.
So, back to the question then: "How is this name transliterated in English?" To that we must say, "It depends on whether or not you're following the Hebrew or Greek! The Hebrew transliterates with an "I" while the Greek does so with an "E". So really, they're both right! (However, Jesus himself is only mentioned in the NT, so, technically, one could also say that the "E" spelling when referring to Jesus is a little more accurate, that is, if you accept that that NT was originally written in Greek.) But still, if you can tell people which one you're using and why at the Christmas party or gathering, they just might be impressed! And if you forget...send 'em here!