It is not possible to say with certainty but I suggest the name may date back to the 18th century when the turnpike act allowed the collection of tolls to pay for road maintenance. Laws passed in 1555 placed the responsibility of road upkeep on the Parish, which may have seemed like a good idea at the time but in practice ineffective. Parishes which bordered a relatively busy road like our Watling Street saw little advantage to themselves in paying for the upkeep of a road that was used by through travellers and as a consequence roads were generally in a bad state of repair.
Oliver Ratliffe, in his book The History and Antiquities of the Newport Hundreds reports:
In the year 1705 this road between Hockliffe and Stony Stratford had become so bad as to be almost impassible. The laws then in force were not sufficient for the "effectual repairing and amending of the same." As the inhabitants of the parishes through which the roadpassed were unable to repair it, being unable to obtain suflicient material for the purpose, except at a great distance from the road, something was needed to remedy this state of affairs, and an Act of Parliament was passed at the commencement of last century, called an "Act of repairing the highway between Fornhill, in the county of Bedford, andthe town of Stony Stratford, in the county of Bucks "
This after 250 years of literally patchy roads was the government's better solution, which was to allow the Parish to charge the users of the road and apply these monies to road upkeep. This Act of 1706 was the first Turnpike Act. The Act set out a scale of charges which entitled the user access to the road from sunrise to sundown.
Every person in charge of a coach, chariot, or calash (a light carriage with movable hood) before passing through it had to pay a shilling, and furthermore, to quote fromthe Act, there were also directions as follows : — " Every waggon, cart, or carriage loaden with grain, sixpence ; every other waggon, one shilling; for every other cart eightpence; and for every horse, one penny. Every chaise with a single horse, sixpence ; every score ofoxen, sixpence ; every score of sheep or lambs, one penny ; and so on in proportion. For every score of hogs, threepence." (from Ratliffe)
I don't want to review the effectiveness of this act or subsequent ones but it did result in a toll bar being placed at Two Mile Ash. Why here? Well it marked the boundary between Wolverton and Loughton on the east side and Calverton and Shenley on the west side. The toll bar would also catch potential users joining the Watling Street from Green Lane as well as those coming from Loughton and Shenley and from the Newport Road. I assume that the tolls collected here enabled travellers to travel the length of the Trust's highway as far as Hockliffe, if they so wished, although in practice distances wouod be shorter for local traffic. The money collected was administered by a Turnpike Trust, comprised mostly of members of the Squirearchy.
I imagine that an ash tree grew on the site, which is a high point on the road, to mark the location of toll bar for travellers. Had it been an oak tree we would have called it Two Mile Oak.