‘Bottle and glass’ is a piece of Cockney Rhyming Slang for ‘arse’. Like most rhyming slang, it works by pairing the target word with a phrase that rhymes with it, then often dropping the rhyming word itself when the phrase is shortened for everyday use. Here the pairing is straightforward: glass rhymes with arse, and the two are usually said together rather than clipped down to just ‘bottle’. It turns up as a plain body-part term, and also feeds into a related put-down, ‘no bottle and glass’, used of someone judged to lack class or style.
What’s the origin of the phrase ‘bottle and glass’?
The exact origin and dating of ‘bottle and glass’ cannot be pinned down with certainty. Michael Quinion’s World Wide Words notes that around the 1920s the phrase ‘no bottle and glass’ was used as rhyming slang meaning that a person lacked class, in the sense of being unimpressive or without style, and that around the same period ‘bottle and glass’ was also used specifically to mean arse. He suggests this second use is likely to have influenced the later, unrelated-sounding sense of ‘bottle’ meaning courage or nerve, as in phrases like ‘has your bottle fallen out?’, though he is careful to describe the origins as misty rather than settled.
Other slang references broadly agree on the 1920s dating but read the wordplay slightly differently. Idiom Origins traces the courage sense of ‘bottle’ back to 1920s rhyming slang in which ‘bottle and glass’ stood for either arse or, in an alternate reading, class. A separate slang dictionary entry, discussing the phrase as still current decades later, hedges further, saying it probably dates back to the 1960s, if not earlier, which shows how loosely the timeline is actually documented rather than firmly recorded in any single early source.
The bottle out entry on this site notes that ‘bottle out’, meaning to lose one’s nerve, is widely supposed to derive from this same rhyming slang for arse, on the logic that losing your nerve and losing control of your bowels are closely linked ideas in everyday speech. No first dated citation for ‘bottle and glass’ itself has been traced, so while the arse and ‘lacking class’ senses are both well attested from the 1920s onward, which came first, and exactly how they relate, remains uncertain.