'Rosie Lee' is Cockney Rhyming slang for 'tea'. Many believe the name came from the American burlesque artist Gypsy Rose Lee, but this is debatable because she was not born until 1911. The expression 'Rosie Lee' was first used in the 1920s.

Cockney rhyming slang is a form of slang that originated in the East End of London. It developed as a way of obscuring the meaning of sentences to those who did not understand the slang. Each term rhymes with the word it represents, but fluent speakers tend to drop the rhyme from the phrase. 'Rosie Lee' became 'Rosie' and it was not uncommon to hear someone ask for a 'cup of Rosie'. Other examples include 'boat' for 'face', because face rhymes with 'boat race'; 'feet' becomes 'plates' ('plates of meat'), and 'money' is 'bread' ('bread and honey').

Many phrases have passed into common language across the United Kingdom and further afield. 'Would you Adam and Eve it?' ('would you believe it?') is a popular example. Others include 'on my Jack (Jones)' ('On my own'), and 'a nice whistle (and flute)' ('a nice suit').

More Info: www.cockneyrhymingslang.co.uk