dirigibles vs. blimps

In many countries, airships are also known as dirigibles from the French (diriger to direct plus -ible), meaning “directable” or steerable. The first airships were called dirigible balloons. Over time, the word balloon was dropped from the phrase. In the modern usage, balloon refers to any buoyant aircraft that generally relies on wind currents for movement, though vertical movement can be controlled in both.

The term zeppelin is a genericised trademark that originally referred to airships manufactured by the Zeppelin Company. Their crafts' names were usually prefixed with the word Luftschiff, German for “airship”.

In modern common usage, the terms zeppelin, dirigible and airship are used interchangeably for any type of rigid airship, with the terms blimp or airship alone used to describe non-rigid airships. Although the blimp also qualifies as a “dirigible”, the term is seldom used with blimps. In modern technical usage, airship is the term used for all aircraft of this type, with zeppelin referring only to aircraft of that manufacture, and blimp referring only to non-rigid airships.

-- Wikipedia