This is what I have in notes on the Hyatt name....I got it from someone else.
"Spelling variation include: Hyatt, Huyet, Hyett, Hyatt, Hyet, Hytte, and others. Hyatt's were first found in Hertfordshire (England) where they were seated from very ancient times, some say well before the Norman Conquest and the arrival of Duke William at Hastings in 1066A.

John Hyatt in Hyatt Heritage, genforum.genealogy.com, 10/28/01 states:
"The name Hyatt comes from the western borders of England, from the County of Gloucestershire. In the local dialect of this area of the word for "gate" is "yat". There are still place names that preserve this spelling pronunciation, such as "Symond's Yat" which means "Symond's gate". "Hy-yat" or High-yat” means "high gate" or hie-gate. A "hie" is another ancient word meaning an enclosure or piece of land protected by walls or fences.
What is the significance of a 'hie yat" or "hie gate"? There are several possible meanings of the name. One is simply a large or high gate at the entrance to a farm or estate. While this is a somewhat common usage, there are two other that may be more significant.
A second meaning of "high gate" or "hie gate" is the main gate of a city, town or castle. Many towns during the Middle Ages were either completely or partially surrounded by a wall. The main gate by which you would enter the city would be the "high (hie) gate" or "hy-yat". Someone who lived by the "hie-gate" such as a gate keeper or "warder" might have the name "Hy-yat".
A third, and probably the most likely meaning, is the gate to an important piece of land or estate. For example a hunting preserve or royal forest would be marked by tall thick hedges or stacked stone walls. The gates that allowed you to enter these areas would be called "hie-gates" or "hy-yats". Some assigned to watch these gates and make sure that only authorized people entered to hunt the king's deer or cut the king's trees would be called "Hy-yat" because his house would be next to the gate.
The reason this third meaning is so likely is that Hyets (or Hyatts--the spelling is interchangeable) held office in Gloucestershire, in the Royal Forest of Dean, hundreds of years ago." Just thought I would pass along.