Meaning

adjective distant but within sight (`yon' is dialectal)

adverb at or in an indicated (usually distant) place (`yon' is archaic and dialectal); ; - Calder Willingham

originFrom French Yon, from the Latin personal name Ionis. Ionis was also named as a daughter of Ἴναχος (Ínakhos), see Ἰώ (Iṓ).

Etymology from Wiktionary, CC BY-SA 3.0