Yes, my remark was not very precise. The two words seem to have different roots ("jarl"/"earl" < Old Engl. "eorl" = "brave man, warrior, leader, chief") vs. ("alderman" = "ald" + "man" = "old man").
Instead of writing:
"during the end of the period the title was shortend into 'earl'"
I should have written:
"during the end of the period 'ealdorman' was replaced by the etymologically unrelated, but phonetically close and shorter 'eorl', that later turned into 'earl'."
What I wanted to say is that "earl", though somewhat anachronistic, can still be an exceptable translation of "jarl". When the emphasis is on contemporary jargon, it might perhaps best be left untranslated. Another alternative would be to translate it with "count", because contemporary Latin sources sometimes use the word "comes" to refer to a jarl; but this translation has its own difficulties because "count" entered the English language also late via the French "comte". The only criteria in favour of "duke" is the fact that this title was later often used in Scandinavia instead of "jarl" for functionally similar offices. Another option is to translate "jarl" with "chief", which corresponds to a more general early usage of "jarl"; however, this would indicate too low a status for most of the Anglo-Saxon period.
My personal preference for the Anglo-Saxon period is to leave it untranslated. If someone insists on a translation, "earl" would still be the best fit in my opinion.
Instead of writing:
"during the end of the period the title was shortend into 'earl'"
I should have written:
"during the end of the period 'ealdorman' was replaced by the etymologically unrelated, but phonetically close and shorter 'eorl', that later turned into 'earl'."
What I wanted to say is that "earl", though somewhat anachronistic, can still be an exceptable translation of "jarl". When the emphasis is on contemporary jargon, it might perhaps best be left untranslated. Another alternative would be to translate it with "count", because contemporary Latin sources sometimes use the word "comes" to refer to a jarl; but this translation has its own difficulties because "count" entered the English language also late via the French "comte". The only criteria in favour of "duke" is the fact that this title was later often used in Scandinavia instead of "jarl" for functionally similar offices. Another option is to translate "jarl" with "chief", which corresponds to a more general early usage of "jarl"; however, this would indicate too low a status for most of the Anglo-Saxon period.
My personal preference for the Anglo-Saxon period is to leave it untranslated. If someone insists on a translation, "earl" would still be the best fit in my opinion.