English
en-
From Middle English en- (“en-, in-”).
The story
Both the Latin and the Germanic forms are from Proto-Indo-European *en (‘in, into’). Intensive use of Old French en-, an- is due to confluence with Frankish *an- and *in- (intensive prefixes), related to Old English on- and in- (intensive prefixes).
Today it means
prefix in, into
Language periods are conventional ranges, not dates for this word.
Etymograph / en-