I would be interested in using a sort of etymological thesaurus. Imagine a normal thesaurus, but with each word in an entry somehow marked to indicate whether it comes ultimately from Latin, German, Norse, Welsh, Irish, etc.
Perhaps this could be done with little icons, or typographical style (Romance words in serif, naturally, Germanic words in sans, Norse in rune-flavoured small caps, Irish in Gaelic script, onomatopoeias and neologisms in Comic Sans). Different but related origins could be conflated or distinguished to some extent (upright serif for Old French, italic serif for Italian and Latin).
Does such a thing exist?
Mostly, I would find this interesting rather than useful. But occasionally, I feel the urge to use a good solid Anglo-Saxon word for something, rather than something French, and this would be the tool for the job. In particular, since I work as a computer programmer, I often find myself needing to name something (a variable, a class, a computer, whatever), and the ability to pick words of different origins for different kinds of things (perhaps Romance for identity classes, Germanic for value classes) would be, if not exactly useful, exactly the kind of pointlessly arch thing which I delight in inflicting on my colleagues.