The word 'tailing' is a deverbal noun formed from the verb 'to tail', which itself originates from the Old English noun 'tægel', referring to an animal's tail. The core semantic concept of the tail as the rear or following part provided the dual modern meanings. In mining, 'tailing' refers to the material that comes at the end of the extraction process—the worthless residue. In surveillance, it denotes the action of following someone, as if attached to their rear. This evolution from a concrete body part to abstract concepts of sequence and pursuit is a classic example of semantic extension within the Germanic word family, with the '-ing' suffix solidifying the action or result into a standard noun.

Structure: tail (follow/end part) + ing (noun-forming suffix) - tail: From Old English 'tægel', meaning the hindmost part of an animal; also used figuratively to mean 'to follow closely'. Its functional role is as the core root conveying the concepts of 'end' or 'to follow'. - ing: A suffix of Old English origin used to form nouns from verbs, indicating an action, its result, or material related to it.