A word translated “now” in the Lament of Akallabêth (SD/247). In the final manuscript version, this is the only form of the word, but in the final typescript version and in all earlier versions, it sometimes appears in the form îdôn.
Some authors have suggested this variation occurs when îdô appears before words beginning in a vowel or semi-vowel (AL/Adûnaic, NBA/12), but this seems unlikely to me. Carl Hostetter, Patrick Wynne and Andreas Moehn instead suggested (VSH/18, AAD/16, LGtAG, EotAL/DAW) that îdôn is a subjective inflection of the word îdô, being used as a noun. The key evidence supporting this second theory is that where the form îdon appears, its gloss is always “now (is)” rather than simply “now”. As discussed elsewhere (SD/429), the subjective inflection can function as the verb “to be”.
I tend to agree with this theory of Hostetter, Wynne and Moehn, but I think the actually development is somewhat more complex. In the first draft version of the Lament of Akallabêth, this form of the word appears twice as īdōn “lo! now is”. As noted by Mr. Moehn (LGtAG), this version of the Lament used a predicate suffix -n “is” in several places: burodan “heavy-is”, rōkhī-nam “bent-are”. It seems likely that draft form īdōn “lo! now is” is another variation of this earlier syntax.
In both draft sentences, the subject is uninflected and the predicate has the predicate suffix -n/-nam. Conversely, in the later sentences the subject is inflected into the subjective case while the predicate is uninflected. This demonstrates the functional shift in the use of the predicate suffix -n in these drafts to the later use of the subjective inflection.
In both the second draft and final typescript versions of the Lament, the form îdôn was retained in all the sentences where it appeared in the first draft. This means that it could have been a remnant of this earlier syntax. The form îdôn could be reinterpreted as the sentence’s subject, but this is also problematic, since îdô is certainly neuter and its subjective form should be *îdôwa, not îdôn.
It is my belief that Tolkien eventually decided that the suffix -n could no longer be used in this context and removed it, switching to an uninflected îdô “now” everywhere in the text as is the case in the final manuscript version of the Lament. On the basis of this deduction, I also believe that the manuscript version was written after than the typescript version.