John William Donaldson, The New Cratylus (Preface):
Many people entertain strong prejudices against every thing in the shape of etymology, prejudices which would be not only just but inevitable, if etymology or the doctrine of words were such a thing as they suppose it to be. They consider it as amounting to nothing more than the derivation of words from one another; and as this process is generally confined to a perception of some prima facie resemblance of two words, it seldom rises beyond the dignity of an ingenious pun, and, though amusing enough at times, is certainly neither an instructive nor an elevated employment for a rational being.
The only real etymology is that which attempts a resolution of the words of a language into their ultimate elements by a comparison of the greatest possible number of languages of the same family. Derivation is, strictly speaking, inapplicable, farther than as pointing out the manner in which certain constant syllables, belonging to the pronominal or formative element of inflected languages, may be prefixed or subjoined to a given form for the expression of some secondary or dependent relation. In order to arrive at the primary origin of a word or a form, we must get beyond the narrow limits of a single idiom. Indeed, in many cases the source can only be traced by a conjectural reproduction based on the most extended comparison of all the cognate languages, for when we take some given variety of human speech, we find in it systems and series of words running almost parallel to one another, but presenting such resemblances in form and signification as convince us that, though apparently asymptotes, they must have converged in the form which we know would potentially contain them all. This reproduction of the common mother of our family of languages, by a comparison of the features of all her children, is the great general object to which the efforts of the philologer should be directed, and this, and not a mere derivation of words in the same language from one another, constitutes the etymology that is alone worthy of the name.