After analyzing the main characteristics of the form and the meaning of idioms, the paper attempts to explore specific idiomatic expressions, some of them coming from a range of genetically related languages, while others do not from a Cognitive Linguistics perspective. The writer stresses the role of cognitive mechanisms –namely, the role of metaphor and metonymy– in the emergence of idioms. Data from different languages are compared to detect possible similarities. Furthermore, the diachronic research brings to light shared patterns of semantic change and shared semantic domains. The writer concludes that many of these similar domains concern negative concepts.