The Greek word—Atakteo—in 2 Thess. 3. 7, translated 'unruly', and 'disorderly', is a military figure used for soldiers marching out of order or out of rank.
The story is told of a proud mother watching the regiment, in which her son was being trained, march past, and remarking to her neighbor: 'They're a fine lot o' men, but they're a' oot o' step except oor Jock.'
(1 Thess. 5. 14; 2 Thess. 3. 7, 11)