Costermonger a secret language, a code which only other costermongers understood. In her book, "Shadows of the Workhouse", Jennifer Worth observed that "Costers... spoke to each other almost entirely in back slang; incomprensible to an outsider." Many costermongers also used "rhyming slang"; where any word can be substituted with another word that rhymes with it. Examples of rhyming slang include: "tin lids" or "dustpan lids" for "kids"; "jimmy grant" for "emigrant"; "apple and pears" for "stairs"; "rubbidy dub" for "pub" and "trouble and strife" for "wife". The selection of rhyming words often suggested a symbolic association. For example, a "sorrowful tale"
Slang terms for money referred to as a "bag" (from the rhyming slang "Bag of Sand"), e.g., £4,000 would be called 4 bags. A "oner" (one-er) has referred to various amounts from one shilling to a pound, to now meaning £100 or £1,000, and a "big one" denoting £1,000. A "oncer" referred particularly to a one-pound note, now defunct. It is also fairly common now in the UK to count backwards from these large denominations using the word "down", e.g. £380 might be "four ton, 20 down" in UK slang. Other rhyming slang expressions for particular quantities of money in the United Kingdom include: