Ha Ha: Origin of This Common Expression

Ha Ha.
Many of us utter it often, and most of us type it or text it, but have you ever wondered just WHERE the term "ha ha" came from?

This one is an exclamation that became a word; and a most peculiar derivative at that. A ha ha is "an obstacle interrupting one's way sharply and disagreeably, a ditch behind an opening in a wall at the bottom of an alley or walk."
 
It is used in English gardens as a boundary that doesn't interrupt the view from inside, and can't be seen from the outside until you come very close to it. It is, in effect, a sunken fence, the inner side of the ditch perpendicular and faced with stone, while the outer side is turfed and sloping.

Photo by Derek Harper

Ha-ha walls are invisible from one's house and make it possible for the whole of the landscape of a garden to appear to be contiguous with the house. 

When these ditches, or fosses, were first used extensively in the 17th century, etymologists tell us that people out for a stroll in the country were frequently surprised to find a sudden check to their walk. Their exclamations of "ha ha!," "ah-hah!," or "hah-hah!" in expressing their surprise became the name of the ditch or sunken fence.

Photo by R. Neil Mashman