Where does “non-dialectal” come from?

non-dialectal (English) comes from English dialectal, from English dialect, from Middle French dialecte, from Latin dialectos, from Ancient Greek διάλεκτος, from Ancient Greek διαλέγομαι, from Ancient Greek δῐᾰ-, from Ancient Greek διά — two.

Ancestry of “non-dialectal”, step by step

non-dialectal traces back through two separate lines of ancestry.

via English dialectal

StepLanguageWordMeaning
1EnglishdialectalOf or relating to a dialect
2EnglishdialectA variety of a language that is characteristic of...
3Middle Frenchdialectedialect
4Latindialectosa dialect; Nihilo lenior in convictores...
5Ancient Greekδιάλεκτοςdiscourse, conversation; manner of speech,...
6Ancient GreekδιαλέγομαιI converse, hold a discussion, debate, argue; I...
7Ancient Greekδῐᾰ-apart; through, across; through; in different...
8Ancient Greekδιάthroughout
9Proto-Indo-Europeandwístwice, doubly; in two
10Proto-Indo-Europeandwóh₁two

via English non

StepLanguageWordMeaning
1EnglishnonObsolete form of none
2Frenchnonno; not; a no, a negative response
3Old Frenchnonno; not; Alternative form of nom
4Latinnōnnot
5Old Latinnoenum
6Proto-Indo-Europeanóynosone; single
Every word from Proto-Indo-European dwóh₁
non-dialectal — Etymology, Origin & Word History | Etymology Explorer