Nevertheless means in spite of that, all the same. Nevertheless, we went, it is nevertheless true, difficult but nevertheless worth it.
It joins two sentences by conceding the first and pressing on with the second, and it takes a comma when it opens a sentence. Nonetheless means the same thing and is slightly lighter. It is three words run together: never the less.
1adverbneverthelessIn spite of that; all the same.
“The hotel was old and small; nevertheless, we had a wonderful time there.”
nevertheless is a connective.
From never the less, three words run together in Middle English.
Middle English
nevertheles
English, today
nevertheless
From Middle English nevertheles, never-þe-les, nevere-þe-lesse. by surface analysis, en + never + the + less; compare never the wiser.
Etymology from Wiktionary, CC BY-SA