yon (adj., pron.)

Old English geon "that (over there)," from Proto-Germanic *jaino- (source also of Old Frisian jen, Old Norse enn, Old High German ener, Middle Dutch ghens, German jener, Gothic jains "that, you"), from PIE pronominal stem *i- (source also of Sanskrit ena-, third person pronoun, anena "that;" Latin idem "the same," id "it, that one;" Old Church Slavonic onu "he;" Lithuanian ans "he"). As an adverb from late 15c., a shortening of yonder.

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Definitions of yon from WordNet
yon (adv.)
at or in an indicated (usually distant) place (`yon' is archaic and dialectal); "scattered here and yon"- Calder Willingham;
Synonyms: yonder
yon (adj.)
distant but within sight (`yon' is dialectal);
what is yon place?
Synonyms: yonder