What is "reboatory"?

Reading my latest Michael Innes story "Stop Press", I came across this in a passage concerning a train journey:-

Timmy's voice and the rattle of the train's subterraneous plunge were alike drowned in an awful and bewildering clamour. A pandemonium of sound, latrant, mugient, reboatory, and beyond all words, reverberated between the walls of the tunnel.

I have managed to run down latrant and mugient but reboatory doesn't appear in any dictionary I have access to; DuckDuckGo reports no results.

Does anyone know what it means?

Solution 1:

Although I also haven't been able to find a dictionary that lists this particular form, it seems fairly clear that reboatory is related to the words reboant and reboation.

The OED defines reboant as "Chiefly literary and poet. Resounding, reverberating; loudly echoing" and reboation as "A resounding echo; a reverberation," and says these come from Latin "reboāre to re-echo".

So "reboatory" presumably is a fancy way of saying "echoing". Since the word "reverberated" is used later in the sentence, you don't actually need to know what "reboatory" means to get the gist (which I assume is intentional, like the famous example where Shakespeare repeats the meaning of the polysyllabic "multitudinous seas incarnadine" with the easier-to-understand "making the green one red").

Using Google Books, I found one other use (that isn't just a mention or disccusion of Innes' use) in New Scientist Vol 82 No 1215, Aug 21, 1980, but the context (a joke about there being an appropriate "-tory" adjective to describe each Tory cabinet member) doesn't make it particularly easy to understand what is meant:

William Whitelaw is, naturally, reboatory.

(p. 632)