I used the roster from the history of the 23rd MVI to create a database covering all its members. I did the data entry for it during my lunch breaks at work.
There it was on the list of abbreviations in the book. “Cordr” meant “cordwainer.” It was an occupation of some sort, but what exactly? I thought that maybe it could be broken down by the syllables and take the sense of the root words. The “cord” part seemed obvious, but what was a “wainer”? Perhaps it was an occupation connected with the place he enlisted from – Salem, a seaport. Sailors were from seaports, and sailors worked with ropes and cordage. Maybe a cordwainer made ropes?
Here is a link to an article I wrote. It represents some of the fruit of my research into the U S Naval Academy and the midshipmen who attended there between 1857 and 1861.