According to many studies on idioms, the most difficult ones are those that are linguistically equivalent but conceptually different. The researcher has collected a number of idioms from English and Arabic that belong to this type with a view to detecting the sources of this conceptual difference based on the Conceptual Metaphor Theory (Lakoff, 1980, 2003) and the subsequent cognitive literature. The source of difficulty is proven to emanate from cultural encoding, including cultural experience, perspective, range, and gesture. The differences in the connotative load of the idiomatic words can also be a reason for the conceptual variance. The study stresses the need for raising conceptual awareness to support language learning
Keywords: Arabic, Conceptual Metaphor, English, Idioms
