I agree that it is "Essex". The word isn't that clear, but if you browse other pages in that set you can see several more entries in that column, that are similar to the one posted and look more obviously like "Essex". There are also a couple of "Suffolk"s and I think an "Orkney" in addition to the more usual "Ireland". Not everyone marked as born outside the county gets this level of detail, though, and it's not immediately obvious why some do. Several census entries are marked as "Lodger" in the left column too, which is a bit unusual. Perhaps some householders volunteered the extra information on their Household Schedule form, and the enumerator transcribed it onto the Enumeration Schedule.
A July 2018 LostCousins newsletter links to a May 2013 article in "The Local Historian" which describes some rare surviving Household Schedules and a comparison to the Enumeration Schedules. Even in a small sample, there was considerable variation in how both forms were completed, and in the amount of information provided.
The householders' and enumerators were instructed to put simply "S", "I" or "F" in this column, for "Scotland", "Ireland" or "Foreign Parts" respectively. This census enumerator (Edward Parsons, according to the same record set images on Ancestry) clearly liked to put a little additional data in his census books. Raise a glass to him. :)