en-

The story

1. Frankish · derived from*an-
2. Proto-Indo-European · inherited from*en“in, into”
3. Proto-Germanic · inherited from*in“in”
4. Old English · inherited fromin-“in, into”
5. Middle English · inherited fromin-
6. Frankish · derived from*in-
7. Latin · derived fromin-“in, into”
8. Old French · derived fromen-
9. Middle English · inherited fromen-“en-, in-”
10. English todayen-

From Middle English en- (“en-, in-”). Originally from Old French en- (also an-), from Latin in- (“in, into”) and Frankish *in-, *int-, *anda-; but also from an alteration of in-, from Middle English in-, from Old English in- (“in, into”), from Proto-Germanic *in (“in”). 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). More at in-, on-.

Words from the same roots