How and why do language and thought arise in the human being? This is, perhaps, one of the questions raised in both anthropology and biology, theology and philosophy. Through a rigorous and eclectic approach, this book addresses not only some of the latest publications on the development of language, but also the symbolism of words, their etymology, their relationship with imagination, memory and, ultimately, with the conception that human beings make of their world and of themselves. The first part reviews the different scientific studies on the relationship between thought and language, as well as some of the archaeological finds that show the process of humanization thanks to the imaginative function and the ability to elaborate concepts. In the second part, the symbolic part of words, essential for the development of thought, is addressed. Finally, the third part breaks down, through etymology and symbolism, the origin of some words, as well as the complexity of the concepts they contain.