Recorded in a number of spellings including Dilnot, Dillnot, Dillnott, Dilnath, Dilnutt, and probably others, this would seem to be an English surname. It is particularly well recorded in the county of Kent, and is almost certainly locational from some 'place'. Unfortunately there does not seem to be any place in the British Isles in any of the known spellings, which still exists, whilst research into the medieval lost village list, has also failed to find a suitable source. The nearest would seem to be Dilworth, a village in Lancashire, which may not be the original source but almost certainly has the same or similar meaning - a place where dill was grown. Dill is still used as a herb to flavour pickle, and was much more so in ancient times. Locational surnames are usually 'from' surnames. That is to say names given to people after they left their original homestead to move somewhere else, and thereafter were most easily identified by being called after their former home. Over the centuries dialects being very strong and spelling very weak, lead to the creation of 'sounds like' spellings. In addition if for some reason the original homestead disappeared, as they often did, there was no marker to correct the spelling. What we can say is that in Kent the surname has been recorded since at least Elizabethan times. Examples include Michael Dillnot, a christening witness at Monks Horton, on March 15th 1571, Alicia Dilnet who married Thoma Dericke (as spelt) at Birchington, on November 11th 1574, and Nicholas Dilnot, a christening witness at St Andrews Canterbury, on November 9th 1666.