Puns by Tolkien

[Morthoron]

One of my favorite puns was elicited by Treebeard, when he said, "There are Ents and Ents, you know; or there are Ents and things that look like Ents but ain't, as you might say."

Interestingly enough, according to the OED, 'en't' and 'ent' are but two of many regional and nonstandard variations of 'ain't' (and from Oxfordshire yet!).

In addition, Tolkien would probably be aware of the following:

The Middle English for have and has was han and hath (the latter form is remembered because the Authorized Version and Shakespeare use it). The way from hath not to hain’t is easy, the more so as -th in hathn’t probably had the value of th- in Modern English this. Dropping one’s aitches and adding them where they don’t belong is a telltale sign of many British dialects, in particular Cockney....

...In late Middle English, ain’t, by being a contraction of both isn’t and hathn’t, played its role very well indeed. As time went on, ain’t began to be used with all persons and came to mean both have not and am/is/are not.

https://blog.oup.com/2006/08/the_much_vilifi/