impair

The word 'impair' entered English in the late 14th century from the Old French 'empeirier', meaning "to make worse". Its ultimate source is the Latin adjective 'peior', meaning "worse", which can be traced back to the Proto-Indo-European root ped- or pes-, conveying a sense of "to stumble" or "to fall", metaphorically leading to a worse state. The prefix 'im-' is an assimilated form of the Latin 'in-', meaning "into" or "against", which here intensifies the sense of causing a negative change. Thus, the literal construction of "making worse" has been preserved in the modern abstract meaning of damaging or weakening something's quality or function.

Structure: im (not) + pair (make worse) - im: Latin origin, a prefix meaning "into, in, on, upon" but in this context, it is an assimilated form of 'in-' meaning "not" or "opposite of". - pair: From Old French 'empeirier', meaning "to make worse", itself from Vulgar Latin 'impēiōrāre', a derivative of Latin 'peior' meaning "worse".