Varro, On the Latin Language VII 1.3
“Therefore, when a man has said many things well about the origins of words, it is better to regard him well rather than to find fault with someone who has not been able to contribute anything. This is especially true since the art of etymology claims that it is not possible to find the origin of all words—just as it is not possible to say why a useful medicine is good for healing. Just so, if I do not know about the roots of a tree, I am able still to say that a pear is from a branch and a branch is from a tree whose roots I do no see.”
Igitur de originibus verborum qui multa dixerit commode, potius boni consulendum, quam qui aliquid nequierit reprehendendum, praesertim quom dicat etymologice non omnium verborum posse dici causam, ut qui ac qua re res utilis sit ad medendum medicina; neque si non norim radices arboris, non posse me dicere pirum esse ex ramo, ramum ex arbore, eam ex radicibus quas non video.