Before these subjects had been undertaken by any half-literate dilletantes, others, the terminology looked more or less like what follows.Aryan was the term sometimes used for any of the peoples and languages within the entire Europe1 and in parts of Asia, to wit, in India ; and a few languages or peoples in some parts near India who are no longer there but are only known from some remnants of the literature.
Questions have been posed whether the term Aryan did not more properly belong only to the Indo-Iranian group. The Sanskrit ariya and the alternate name of Persia, i.e. Iran are from one stem-word, meaning, of persons, 'the noble ones', this probably derived from the sorts of physical phenomena in the English called shine.
The distinction may be valid, this looks rather like some sort of a side-issue and only some consensus on some consistent usage, one way or the other, among the writers might be needed.
Please note that the ethnic (or, more exactly, genetic) matters are capable of being thoroughly distinguished* from the linguistic matters. (Proofs : any average human being can learn any language or any kind of language into which he or she might happen to be born. In addition, many people have been able to learn and to master other languages than were native to them.)
* Also note that these matters have been often confounded as thoroughly as possible, entirely deliberately by certain sorts of "specialists".Considering only the linguistic matters, all this has something to do with the entire literature in any and every one of the languages involved. This is not really some small amount of knowledge on somebody's local or particular issue (which only interests a few specialists). This also has to do with the living languages of, it seems, the majority of the Humanity 2008.
If the generalised import of the term Aryan be considered, then the three terms, Aryan, indogermanic, Indo-European were exactly synonymous; any one of the three terms has been used to represent any of the languages involved or the entire group of languages.
The term 'indogermanic' has been most often used by the German writers. This is not incorrect but has been, as was the case with ultimately any one of these terms, arbitrary.
Illustration : the term 'indogermanic' may be just as good as would be such terms as, e.g,, 'indo-iberian', or' 'indo-celtic', or, 'indo-slavic', or, 'indo-romanic', etc. The precedent notion of the Græco-Roman civilization meant roughly almost the same thing — except that similarities and actual links had been discovered sometime in the 18th century with the languages of Persia, India, eventually Armenia, etc. By generalising from the 'Graeco-Roman' and following the historic course of the research one could perhaps just as well speak about the Indo-Graeko-Roman civilisation.
Any one of these three terms, i.e. aryan (Aryan), indogermanic, Indo-European have been valid terms, and numerous instances of valid (intelligible) usage can be found in the literature. In the end, the term 'indoeuropean', or, Indo-European, might presently seem the most readily acceptable one, in part also because of certain irregularities introduced by some dilletantes, others, during the 20th century.
Of the authors notable on these subjects were : Sir William Jones in England, Franz Bopp in Germany, Fr. Miklosich in Slovenia, Michel Breal in France, Aleksander Brückner in Poland, etc. (This is not a sufficient list but a sort of "off the top of my head" collection. Every one of those given seems to have been very important and there have been many others).
WPT, March 08
1. Except the peoples (and languages) in Finland, Estonia, Hungary who are of the Turanian origins. I gather that also the Basque are another, altogether separate group, who might be a survival from some times really remote (so far as I know).