USAGE: YAEUT: "proper"

The inspiration for these questions is the following observation:
In American writing, the German terms "eigenvector" and "eigenvalue" are
sometimes translated as "characteristic vector" and "characteristic value", but
those are such mouthfuls that usually the German terms are just borrowed as-
is.
But in British writing, the terms are often translated as "proper vector"
and "proper value", and these compete favorably with the barely-modified
German words.

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So, here the question:

In what circumstances do UK speakers often use "proper" where a USA
speaker would use "own"?

Is such usage old-fashioned now in the UK?  Or is it still current in some
speech-subcommunities?

Are such usages limited to just parts of the UK?  For instance, just Great
Britain? or just England?

Or do they actually also occur in other English-speaking countries?

Does Canadian English more closely resemble UK English or USA English in this
regard?

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Thanks in advance to anyone who knows anything about any of these
questions.

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