also fogy, "an old, dull fellow," 1780, Scottish foggie, originally "army pensioner or veteran," perhaps connected to fogram (1775) "old-fashioned person;" or from fog in obsolete senses of "moss" or "bloated fat" (1580s).
[origin uncertain; perhaps fr French fougeux, ''fierce, fiery,'' referring to the doughty spirit of an invalid soldier, whence fogy, ''fierce, fiery,'' found by the 1860s; veteran soldiers were called foggies in the late 1700s, perhaps because they were regarded as moss-covered with age, fog being Scots dialect for ''moss'']