[Irouléguy] Doesn't the prefix 'en-' mean something closer to 'to make'? (Enlarge - to make sth large).
Actually, the example that made me think that was ennoble - to make noble.

I have on my lap a big Chambers Dictionary:

en- prefix
1) in words derived from Latin through French (a)used to form verbs with the sense of in, into, upon; (b) used to form verbs with the sense cause to be; (c) used intensively or almost meaninglessly;
(2) in words derived from Greek used to form verbs with the sense of in.

I can't think of any for sense (c)...

(Knobbly) I think enliven could fall into your category (c). Liven would do on its own ( = to make lively).

The Simpsons also introduced "enbiggen", iirc.

[CdM] Wasn't that EMbiggen? As in, "A noble spirit embiggens the smallest man" or something to that effect?