Thelma

My family has used the name Thelma since 1580. My daughter is Thelma as it was my mother as it was my grand grand... grandmother born in 1580. The name Thelma comes from the Greek word "Thelima" that means errand. The word Thelima is used in Orthodox religion and describes the willingness of the God as "Gods thelima". During the centuries the letter "i" disappeared and the word transformed to "Thelma".

The girl-name Thelma comes from the boy name Anshelm, which is of Germanic origin (do not read "German" but "North-European") and has been used since early middle ages: 6-7th century, maybe even before.
Anshelm has been quite popular in 19th and early 20th century in France under its form "Anselme".
We get to the meaning by chopping the name up in two bits: Ans and Helm.
In ancient Germanic Ans meant god(s) and/or divinities and Helm meant helmet or protection.
So the name means "protected by gods" or "divine helmet", something like that.

Your origin date is off by at least decades:
In the book 'Boney Fuller: Soldier, Strategist, and Writer, 1878-1966' by Anthony John Trythall, On page one Fuller's Mother's birthdate is given as 1848, her name 'Thelma'.

Though I currently cannot shed light on the origin of the name "Thelma", I can state most authoritatively that the name was not invented by British author Marie Corelli for her 1887 novel. Miss Corelli was born in 1855. The 1850 census for the United States lists at least 35 women bearing the name "Thelma", several of whom were born in the 1700's. This list would include only a fraction of women actually named "Thelma", since some women were not listed at all, some were listed only by initials, and most were listed by first and last names only, omitting middle names of "Thelma". While the number hardly compares with such common names as "Mary" or "Elizabeth", the name was most clearly in use a hundred years (and possibly much more than that) before Miss Corelli wrote her novel.

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As this was my mother's name, and before that, the name of an aunt, I am interested in the correct origin and will research further. I will share whatever further factual information I can discover. Thank you for the opportunity to clear up this myth. [noted -ed]

Personally I think it's quite unlikely that Marie Corelli created the name Thelma from a Greek word for "will". Thelma doesn't seem to be described as willful, strong-willed, or stubborn anywhere in the novel. Instead Corelli makes the _sound_ of Thelma one of the themes in her novel. Here is a quote from what the hero (who eventually marries Thelma) thinks about her name shortly after he meets her:

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"Just the sort of name to suit a Norwegian nymph or goddess. _Thelma_ is quaint and appropriate, and as far as I can remember there's no rhyme to it in the English language. _Thelma_!" And he lingered on the pronunciation of the strange word with a curious sensation of pleasure. "There is something mysteriously suggestive about the sound of it; like a chord of music played softly in the distance."

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And Corelli was a popular author, not an especially literary one. Though she had delusions of grandeur and fancied herself another Shakespeare, it seems unlikely she'd be searching out words in a Greek dictionary in order to name a Norwegian character. I think she created it as a brand new word because she liked the sounds it contained, and it has no meaning beyond that given to it by the history and personality of the character in her novel. :)
[noted -ed]