More like "notwendigerweise". "Notwendig" can't be an adverb, I think. At least in this case it would be impossible.
Is there a way to remember this word easily? I can usually split them into smaller bits that look like words in other languages I know, but here I get as far as nöd->need and then I'm lost.
After playing around in Wiktionary.org etymologies, I came up with this possible mapping of the root syllables from Swedish to English. Maybe it will help. Or not.
I get a literal root-for-root translation of "need-wend-y-wise", meaning something like needfullywise.
nöd = English "need"
vänd = English slightly archaic "wend" (as in turn); I wend my way home. I think it's used to make an adjective implying something like "having the quality of". Modern English is more likely to use -ful in that capacity.
ig(t) = Swedish adjective suffix that maps to English adverb suffix "-y"
vis = Swedish adverb suffix that maps to English suffix "-wise", meaning "in the manner of", as in clockwise
I haven't been able to split this up into more recognisable bits myself, I just have to train myself to recognise the word when I see it. One mnemomic you can use is "a friend in need on your TV" here ... "nöd" + "vän" + "dig" + "TV"... admittedly the word for friend has nothing to do with the origin of the word (nor does the placement of "dig" here have anything to do with "you"), but if you can keep this in mind, it is a cool way to learn this word.
Amusing myself by trying to sing it to "It Ain't Necessarily So" (from Porgy and Bess). Works kind of.
That’s not how you say the expression, just as you don’t say necessarily not in English.