Note: Do not rely on this information. It is very old.
HH, the eighth letter of the alphabet, is the Phoenician letter cheth, the value of which was the same as that of ch in the Scotch word loch. Both the Greek "rough-breathing" and the Latin H were derived from cheth. In Anglo-Saxon H was still a guttural, but it afterwards became a spirant. In English it has disappeared before many words beginning with a consonant, as loaf, neck, ring, and is (in South Britain) scarcely heard in the combination wh, which was originally hw, but to this rule the word who forms an exception. In French, Spanish, and Italian it has been entirely lost, although in the first two the character is retained. In German musical notation the letter H denotes B natural, the letter B being used for our B flat.