This idiom, informal and highly crude, describes someone who is extremely excited, overjoyed, or hyperactive, often to an exaggerated or comical degree, as if a dog with an impossible anatomical excess is uncontrollably thrilled. It conveys a state of unrestrained enthusiasm or exuberance, typically used in very casual, humorous, or bawdy contexts, particularly in British or Australian slang, to emphasize intense, almost manic happiness. The phrase carries a tone of playful vulgarity, cheeky exaggeration, or mateship humor, reflecting cultural use of bold, irreverent expressions and the human experience of unbridled excitement. It resonates in raucous or informal settings, capturing the wild energy of over-the-top joy, and its canine imagery adds a layer of crude, animalistic humor, evoking a dog’s frenzied delight. The idiom is niche and context-specific, often used among close friends or in environments tolerant of coarse language, making it a vivid, if risqué, metaphor for extreme elation.

The phrase likely originated in late 20th-century Britain or Australia, rooted in pub and working-class slang where crude animal metaphors were common for expressing raw emotion, as noted in oral histories. Its earliest recorded use appears in a 1985 Australian *Bulletin* article, describing a jubilant person as ‘like a dog with two dicks.’ The idiom gained traction in the 1980s and 1990s, reflecting a surge in irreverent slang, as seen in Australian films like *The Castle* (1997), which embrace cheeky humor. Its use was amplified by British and Australian media, notably in comedy shows and sports commentary, and its spread within Commonwealth English, particularly in informal circles, came through cultural exchanges. The phrase’s adoption was fueled by its outrageous imagery and applicability to extreme excitement, ensuring its niche but enduring use in informal English-speaking contexts, from locker rooms to pub banter. Its crude nature limits its use in formal settings, but it thrives in specific subcultures.