Why can you email an email but you can't letter a letter?

A commenter on my recent blog post suggested that I blog about the fact that you can blog a blog, and then followed it up with the question 'Why can't you letter a letter but you can email an email'? 

Blog as both noun and verb is another instance of the process I mentioned a while back, the nounification of verbs or the verbification of nouns (that's not the real name: it's called 'zero derivation' or 'conversion', but that's dull). The process goes both ways, but you get different results. If you turn a verb into a noun, it's an instance of the action: a kick is an instance of kicking. If you turn a noun into a verb, you can't always say what the meaning will be: to fish means to catch a fish, to trouser means to put something into one's trouser pocket and to book means to make a reservation or charge with an offence, and so on. Here I think we've got noun to verb, and I'm fairly certain that this is supported by the date of the earliest appearances of the noun (which derives from weblog) and the verb, though that can be tricky to verify.

Back to blogging a blog and lettering a letter. It's quite unusual that the noun can be an object of the verb derived from it. I can't really think of any examples other than the ones given above, and maybe text as in text message. Maybe message itself. I don't know if it's important that these are all communication acts... you can shout a shout, I suppose, and whisper a whisper. 

In US English, the verb is more commonly mail, whereas in British English post is used. But in the US I don't think that mail is used for one particular letter, so you can't mail a mail. When email was invented, the word email was used, probably by analogy with mail, for the general process/system. It quickly became used as the name for a particular message sent by email, as no specific word for this item existed, and for the verb, by the same process of verbification. Thus you could email an email. 

You can't letter a letter because there already exists a verb post, or mail if you prefer. We could, when email was invented, have broadened the sense of post or mail to include sending an email, but we didn't, perhaps because it seemed quite different (and in British English, the verb post is not even the same as the one used in email). Post (or mail) likewise would have blocked the use of letter as a verb - but the plausibility of all this is dependent on when each was first used. 

So in short, my answer is: because there is already the verb post but there is no equivalent verb for the use of sending an email or writing a blog other than the generic-verb+noun combination like send an email. 

Pub crawling

There's a game for various iDevices called The Simpsons: Tapped Out, in which you have to rebuild Springfield. It's good; I'm obsessed. 

Every now and then it gets seasonal updates, and today it got an update for St Patrick's Day, which seems to be a bigger thing in the US than it is in England, where no one particularly cares about it. (I expect they do in Ireland.) Anyway, in the game, to introduce the new storyline, Homer says this: 

Notice that he says 'The day we all pub crawl to celebrate St Patrick', using 'pub crawl' as a verb. This strikes me as ungrammatical. I'm quite fascinated by this because 'pub crawl' must certainly be a British expression, borrowed into US English for the purposes of British-style (or perhaps Irish-style, in this case) pub crawling. It's my impression that in US English, the usual term for a drinking place is a 'bar'. We do use this word in UK English too, but it's not used for the more traditional pub-type places, only for the trendier type of establishment. And of course it is the place in a pub where one is served.

So what of this 'pub crawl' verb then? Well, the origin of the expression is clear: a compound noun was formed from a zero-derivation of the verb 'crawl' plus the thing that is crawled, to indicate an occasion of 'crawling' pubs. Zero-derivation is when you change the category of a word without changing its form, and is fairly common in English for the purpose of verbing nouns and nouning verbs. This noun 'pub crawl', however, seems to have been zero-derived back again into a verb in Homer's idiolect. I don't think compound nouns are very commonly turned into verbs at all in English: we have lots of compound nouns from verbs, like tin-opener, but hardly any verbs ('babysit' is an example, backformed from 'babysitter'). In fact, Homer seems to be particularly fond of them. In my morphology class, I use an example from the Simpsons of a very rare instance of a process called 'noun incorporation', and this is an exactly comparable example, also spoken by Homer:

Did I ever tell you about the time I babyshot my boss?

Here, the instrumental noun 'baby' is incorporated into the verb, giving a complex verb 'babyshoot', meaning 'to shoot someone via one's baby'. What I want to know is who in the Simpsons writing team is putting these verbs into Homer's language? I'm a big fan of their work, whoever they are.