From Elizabeth Daingerfield Zwicky’s blog, about her daughter (age 5):
… we were discussing mangos. Opal said they grew on bushes, I said they grew on trees. I cited Mangaboom as a source; she pointed out that it was a story. So I went to the Internet! On my phone. She was OK with the pictures of mango trees, but what she was fascinated by was the process of making the picture bigger. “Hey, can I bigger it?” she said. I explained that “bigger” made sense, but we say “enlarge”. She said, quite patiently really, “Can I enlarge it? And then ensmall it?” Boy, was I sorry to explain that the opposite of “enlarge” is, of all things, “reduce”.
It’s not just little kids. You can find some hits for bigger ‘enlarge’, mostly (but not entirely) in computer contexts. For instance:
How did you do that neat texturing? It really DOES look like an adobe wall, I clicked on the pic to bigger it and it looks very cool! (link)
And yes again, 3D glasses will actually work on this (red on your left eye, blue on your right). Oh, and as always, click to bigger it: … (link)
i am 16 and my penis is 13 cm and quite thin.i am quite tall for my age. is my penis going to grow any more? what can i do to bigger it? LENGTH AND WIDTH … (link)
As for ensmall, there are cites where it’s clearly treated as an innovation:
What is more logical than the opposite of ‘enlarge’, namely ‘ensmall’. There are many things in our daily lives that we might want to make smaller – cars, … (link)
in our families find ways to ‘ensmall’ rather than enlarge our spending, and make our presence rather than presents a sign of our interest and love? (link)
But there are other occurrences. OED2 has an entry for ensmall, though it’s marked as rare, and the dictionary has only one cite:
1857 THOMSON Land & Book IV. xl. 612 To reconcile my previous anticipations with the vastly ensmalled reality.
And it still crops up, again mostly in computer contexts:
For them and for anyone else who needs to ensmall a detailed image, here’s my amateur recipe for generating good thumbnails via PhotoShop: … (link)
This is a Craigslist ad that seems to be real. I’m going to ensmall it at the bottom in case the URL doesn’t persist. (link)
Bigger ‘make bigger, enlarge’ is a (causativizing) verbing of an adjective, a comparative adjective at that. Verbing of adjectives in English is usually affixal (as in en-large, damp-en, modern-ize); zero derivation is rare. But kids are fond of zero derivation (of all sorts), and for good reason: it allows them to expand their vocabulary at essentially no cost.
Ensmall is a more sophisticated innovation, verbing the adjective small via the prefix en- (a pattern that is not productive in English). But it’s a natural innovation, created on analogy with enlarge (and exploiting the opposition of large and small), which is transparently what Opal, having just been offered the model enlarge by her mother, did.
There are several other possible verbings of small: zero-derived small, suffixed smallen, doubly affixed ensmallen, suffixed smallize. All of these are non-standard, but all are attested — a tribute to people’s fondness for regularity.