and if we consider that the same process must have gone on with the words of our mother tongue from childhood upwards, we shall clearly see that the earliest learnt and of-tenest used words, will, other things equal, call up images with less loss of time and energy than their later learnt synonyms.
Spencer states that the simple words we first learn as children are more efficient than the synonyms we learn later in life. There are less connections to be made with the original word that we use, and therefore using original language is more economic.