I'd heard of 'upper case' and 'lower case', obviously, but not of 'camel case' until our web editor enlightened me recently.
It's one of a number of names for the practice of using capital letters in the middle of (usually compound) words – 'iPod', for example. The capital letter is said to resemble the hump of a camel.
As you can imagine, camel case is popular in brand names and unpopular in subbing circles. In fact, you could say that having to remember or constantly check strange capitalisations gives subs the hump!
The Wikipedia article on camel case (or more appropriately, CamelCase) is rather good, so I'll just point you over there today.
4 days ago