The word 'underhand' is a transparent compound from Old English elements, directly combining 'under' and 'hand' to describe a physical position. Its literal sense, referring to an action performed with the hand kept low (as in an underhand throw in sports), is a straightforward spatial metaphor. The figurative meaning of 'secret' or 'dishonest' evolved from the idea of actions being concealed 'under the hand' or done in a sneaky, low manner, contrasting with the 'aboveboard' or open-handed conduct. This semantic shift from a physical descriptor to a metaphor for covert behavior illustrates a common pattern in English where spatial terms acquire abstract, evaluative meanings.

Structure: under (beneath) + hand (body part) under: From Old English under, meaning "beneath, among, during." It is a preposition/adverb of position. hand: From Old English hand, meaning "the terminal part of the arm." It is a noun referring to the body part.