(Darren) "Enlarge" is from the French enlarger and may just be a copy, so to speak. A more regular formation, reading between the lines of my 1964 COD, would be "largen", (cf thicken) the prefix en- + adjective being rare. En- + noun or verb is common though and explains "enliven" either as "to give life to" or to (intensively) liven.

[Rosie] ...which has both prefix and suffix. As does embolden. But you can't ensticken the affixes on ad lib.

You people scare me a bit sometimes. I love you all, but you scare me mildly.

(Raak) With "embolden" and "enliven" it would seem that in the past someone has done just that. I don't think the rules are particularly well-defined. (nights) Yep, we're a bunch of swivel-eyed fundamentalists. In the beginning was the Word. AND THE WORD SHALL BE SPELT PROPERLY. :-)

P - R - O - P - E - R - L - Y

Is there an opposite for "enlarge" which has the same pattern? There doesn't seem to be an "ensmall" or "enlittle" (although there is "belittle" but then where's the "belarge"?) - the closest in meaning is probably "shrink," which seems to have no connection with any words meaning "small" whatsoever.