In the case of the vast majority of words, before we can begin by comparing one word with another, or trying to discover the root-words of several different languages, we have first to trace the history of these words backwards, each in its own language, and find their most primitive forms. But in tongues which are pretty nearly related we have often no difficulty in seeing the similarity of corresponding words just as they stand to-day. We have no difficulty, for instance, in seeing the connection of the German _Knecht_ and our _knight_,[22] the German _Nacht_ and our _night_, the German _Raum_ and our _room_; or, again, the connection between the Italian _padre_ and the French _père_, the Italian _tavola_ and the French (and English) _table_, etc. But where the connection between languages is more distant, we have more and more to go back to much simpler roots, in order to show the relationship between them; and by a vast majority the primitive root-sounds in any large family of languages are single syllables, whereof the most constant parts are (as a rule) the consonants. So far as our knowledge goes, we might think of man as beginning human speech with a certain number of these simple root-sounds, and then proceeding to ring the changes upon these root-sounds to express varieties in the root-idea. Sometimes it is easy enough to trace the connection of ideas between different words which have been formed out of the same root-word. But sometimes this is not at all easy. Nor can we say why this special sound has been adopted for any one notion more than for a number of others to which it would have applied equally well. From a root, which in Sanskrit appears in its most ancient form, as _mâ_, ‘to measure,’ we get words in Greek and Latin which mean ‘to think;’ and from the same root comes our ‘man,’ the person who measures, who compares, _i.e._, who thinks, also our _moon_, which means ‘the measurer,’ because the moon helps to measure out the time, the _months_. But how arbitrary seems this connection between _man_ and _moon_! So, too, our _crab_ is from the word _creep_, and means the animal that creeps. But why this name should have been given to crab rather than to ant and beetle it is impossible to say. So that there appears as little trace of a reason governing the formation of words out of root-sounds as there appeared in the adoption of root-sounds to express certain fundamental ideas.