Souped-up Definition

adjective

(horse racing, cant) Of horses injected with something to make them run faster or change their temperament (19th-early 20th century)

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(US Navy, slang) Drunk.

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(of an engine, a motor vehicle or another device) Modified for higher performance (likely derived from the horse-racing term)

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(Rhode Island, Massachusetts, Connecticut, slang) Excited.

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verb

Simple past tense and past participle of soup up.

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Origin of Souped-up

However, this is antedated by usage in horse racing cant that applies the term to horses, and by a US Navy euphemism for drunkenness. The former is attested in Webster New International Dictionary (1909) and the latter in Our Navy (May 1915). Both may be figurative interpretations of soup as a liquid food item, although other origins cannot be discounted.

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Automotive and aviation usage is attested at least since 1925 (in Popular Mechanics) — possibly from 1921 — with even early citations linking it to supercharged. Therefore, it is often contended that soup is a clipping of super.

From Wiktionary
Etymology is unclear, although it is a past participle form from the verb soup.

From Wiktionary