The surname Ledwith is a derivative of the name Ledwich this change of the "t" and "c" occurs in many instances with the use of the "t" becoming more common in the 20th century. Earlier variations are mainly due to the fact that pre 1800 less than 5% of the population could read or write and those who could spelt their names differently on various occasions.

From around 1570 onwards two types of handwriting emerged. There were the" Secretary Hand" and the "Italic". During the seventeenth century the secretary hand was the most popular but from 1700 onwards this died out. The secretary hand is responsible for the interchange between ‘t’ and ‘c’. An example of the secretary hand for ‘c’ and ‘t’ is shown below.

This confusion in spelling, as well as local dialects when the name was passed by word of mouth, would have changed the way the name was written and copied.

Ledwich in turn has devolved from "Ledwyche". Other variations that can be traced back to this source are Ledwitch and Ledwidge. These variations have developed as the language has changed over the number of years, especially as names were written phonetically hence further variations such as Leadworth and Ledworth but not Ledwick (see later).

In many instances in the 1800s the name is written as Sedwith. This is due to the style of writing where newly literate clerks wrote the "L" resembling an "S" and subsequent copying has chosen the wrong option.

The similarity between the Irish coats of arms for the two names also shows the practice of interchanging and additions to the spelling of the name.

The family was first documented as coming from Saxony. The first documented evidence being a Roger de Ledwyche. A number of Normans were at this time were taking over land from the Saxons defeated at Hastings. Roger was the owner of land in the Shropshire area around 1221. Very few Normans had hereditary surnames prior to Hastings and those that did were only 2 or 3 generations old. The majority of the nobles obtained their names from the areas they were given land in "nom de terre". This practice was also copied by the lesser nobles and Roger took his name from the place in Shropshire called Ledwyche which is mentioned in the Doomsday book. The use of "de" in the surname is the Norman equivalent of "atte" meaning "from the" or "from" and has undergone the fate of disappearing from the name. The are two places near Ludlow in Shropshire, Upper Ledwyche and Lower Ledwyche and currently it is uncertain which is the origin although they are close together.

It is uncertain if Roger was a knight ""cniht" or a "discthegn" steward. As both would be taking over land at this time. The average landed base for the lessor folk at this time was 1½ hides. This represented about 120 acres giving an income of between 30s and £2 per annum. This would be enough to sustain a night but not nobly. This meant that Knights and prosperous peasants had about the same income. These holding were known as "berewicks" and belonged to the Lord of the Manor.