Middle English word eken comes from Proto-Indo-European *h₂weg-, Old English īecan, and later Proto-Germanic *aukaną (To increase, to grow.)

Detailed word origin of eken

Dictionary entry	Language	Definition
*h₂weg-	Proto-Indo-European (ine-pro)
īecan	Old English (ang)
*h₂owg-éye-	Proto-Indo-European (ine-pro)
*aukaną	Proto-Germanic (gem-pro)	To increase, to grow.
ēacan	Old English (ang)
eking, eching	Middle English (enm)

Words with the same origin as eken