The term 'washed-up' originates from the literal nautical imagery of debris or flotsam being deposited on a shore by the action of waves, a process completed and final. The core verb 'wash', with Proto-Germanic roots, combines with the completive particle 'up' to form a phrasal verb meaning "to bring or be brought to an end on the shore." This vivid physical metaphor was semantically extended by the early 20th century, particularly in North American show business slang, to describe a person whose career has been concluded and left behind, much like detritus on a beach, conveying a sense of being finished, obsolete, and no longer viable.

Structure: wash (to clean with water) + ed (past participle suffix) + up (completive particle) wash: From Old English wæscan, meaning "to cleanse by ablution"; functions as the core verb. ed: A Germanic suffix forming the past participle, indicating a completed action or state. up: From Old English up, upp, meaning "aloft, on high"; functions as an adverbial particle denoting completion or finality.