An Ait (or Eyot) is a small island in the middle of a river or lake - such as those that are found along the River Thames in England between London and Oxford. Aits are typically formed by the depositing of sediment in the water, which accumulates over a period of time. An ait is characteristically long and narrow, and may or may not become a permanent island. Aits may be eroded: the resulting sediment being deposited further downstream and resulting in another ait.
But why the difference between Ait and Eyot? There's no obvious logic from the relative locations. Heading upstream from Hammersmith Bridge, the sequence goes like this....
Chiswick Eyot
Brentford Aits
Isleworth Ait
Eel Pie Island (not an Ait?)
Trowlock Island
Stevens Eyot
Raven's Ait
Thames Ditton Island (now I know some Gabriolans who lived there...)
Tagg's Island
Garrick's Ait
Platt's Eyot
..... and so on.
No logic, no pattern (there are Aits and Eyots close to both banks of the river, so it's not a Surrey thing or a Middlesex thing.) No, it seems likely that it's down to the vagueries of Old English - and only those who staked claim to the fragile landfall could determine which it was to be.
So when is an Eyot not an Eyot? When it's pronounced "Ait" of course!!!
Confused? I am. Can anyone shed any light on the difference?