In a speech last night, Mervyn King discussed the separation of retail and investment banking; a British version of the American Glass-Steagall Act.
A random thought occurred to me. Retail banks have customers, like most other businesses. Investment banks, though, have clients, like lawyers, accountants, management consultants and….erm….prostitutes.

Lol!
Flicked to an online dictionary and found
1350–1400; ME < L client-, s. of cliēns person seeking the protection or influence of someone powerful; perh. akin to clīnāre to bend (see incline )