My question has to do with the spelling as well as pronunciation of two words: 'word' and 'work'. I guess that work comes from OE weorc. After loss of the diphthong, some dialects preferred the sound o and others the sound e. Logically, the present-day english term is pronounced with long relaxed e but has the spelling O. Is it the right explanation? Furthermore, what happens concerning 'word'.
Thanks for your attention.
Your good question is complicated by three different things: (i) work had many different earlier spellings (the OED lists almost forty), (ii) the [r], as usual, had a radical effect on the preceding vowel sound, and (iii) the [w] had an equally radical effect on the following <or>.
Our noun work is assumed to derive from OE weorc, though some dictionaries also refer to the other OE forms werk, werc, and worc as possible sources, which suggests that the <eo> diphthong had simplified quite early on, with, as you say, some dialects tending to pronunciations with the vowel spelled <o> and some tending to pronunciations with the vowel spelled <e>. The OED also lists forms with the vowel spelled <a>, <i>, and <u>.
The earlier forms like werc and werk, with [e] spelled <e>, would have fallen in with a large group of words in which [er] came to be pronounced with a syllabic [r] – that is, with a loss of vowel color and a more or less pure [r] sound providing the peak of the syllable, as in her, herb, jerk. The reduction to a syllabic [r] occurred because in such words, when pronouncing [e], the tongue was retracted slightly in anticipation of the upcoming [r]. This retraction leads to a sound much like what I think you mean by a relaxed <e>, which in time can become indistinguishable. In the case of later [r]-dropping, as in much British and some American English, the vowel sound is well described, as you say, as a long relaxed <e>.
Other such reductions include [ir] to [r] (bird, sir, thirst) and [ur] to [r] (blur, curl, purse. This syllabic [r] also occurs in words like earth, pearl, journey, myrtle, etc. (There is more on this reduction in American English Spelling, pp. 321-26, where it is called “The [ur] Convergence.” For a more detailed and technical discussion, see volume two of E. J. Dobson’s English Pronunciation: 1500-1700, pp. 746-59.)
The reduction to what I’m calling syllabic [r] is common in American English, though dictionaries show it as [ûr] or schwa+[r]. And some dialects of British and American English still retain at least some of the vowel color at least some of the time.
Earlier forms like worc, worke, work with [wor] would also have fallen in with this same reduction, for although words with <or> usually retain some sort of <o> sound, those with initial <wor> often reduced to the syllabic [r] – as in world, worse, worth, worry and work.
The situation with word is similar but simpler. It comes from OE word with initial [wor] and thus would experience the same reduction to syllabic [r].