Idiomatic and proverbial expressions are important components of the oral tradition of Sesotho sa Leboa, and therefore a knowledge of the literal meaning of words as they appear in dictionaries without inclusion of their figurative meaning seems to be a shortcoming. An idiom or a proverb possesses one basic meaning, i.e. the meaning to which the idiom or proverb is basically meant to refer, but each idiom or proverb is made up of several lexical items. Each of these lexical items has its own meaning, which usually differs from the figurative sense of the idiom or proverb. Even though the meaning of the words in an idiomatic or proverbial expression seems to differ from the sense of the idiom or proverb, there is to a certain extent a relationship. It is this relationship which lexicographers can assist to explain in their definitions in order to clarify both the literal and the figurative meanings of words in Sesotho sa Leboa. This article aims to stress the importance of having specialized dictionaries which will give users detailed etymological explanations of the meaning of idiomatic and proverbial expressions as used in Sesotho sa Leboa. The etymological analysis of the meaning of these lexical items (idioms and proverbs) will provide a better understanding of these expressions and enrich dictionaries with detailed definitions. This will create a better understanding of the relationship between the literal meanings of the expressions and their real (i.e. figurative) meanings. Keywords: diachronic analysis, etymology, figurative expression, idiom, lemmatization, lexicology, metaphor, metaphoric expression, proverb, synchronic analysis, terminography.