It struck me that in both cases, and especially taking them together, this had the ring of a set phrase. But what were its connotations? So, I hastened to Google Ngram to seek it out (in both spellings). Here are the results for their German corpus:
It's notable, first, that the phrase "echt deutsch" doesn't show up at all before around 1815. Then there's a gradual increase in its use through the nineteenth century, which presumably reflects the growing nationalist movement and unification. What counted as German must have been something discussed a lot at that time. But by far the biggest spike is around the end of the Great War - I wonder why? (Eliot clearly had his finger on the linguistic pulse, at least.) And only a relatively modest revival during the 1930s, when one might have expected a vigorous resurgence.
Now here are the charts for British English:
And American English:
(Note that the scales are different - the phrase was significantly more common in Britain than in the USA.) In both charts they're pretty inconsistent about the case of 'deutsch' - Forster clearly wasn't alone in applying English capitalization conventions. The Americans have a big spike at the end of the first War, much as the Germans do - perhaps in part reflecting immigration to that country? Both countries - but especially the British - go to town with it during the Second World War, where it presumably acquires propaganda value. Presumably too a good few of the instances in both these diagrams occur in discussions of either The Waste Land or Howard's End.
I thought I'd share these charts because they intrigue me, but I have more questions than answers. It's hard to hear 'echt deutsch' other than through the filter of Nazism, but did it always have the whiff of racial purity? Was it, in fact, always applied to people - as opposed to (for example) culture?
Feel free to leap in.