Abbreviations beginning with the letter I

ibid. – ibidem (Latin), in the same place
IIGS – International Internet Genealogical Society
Inf. – Infantry (US military regiments)
inf. – infant
int. – intentions, public notice of an upcoming marriage
IGI – International Genealogical Index, created and maintained by the LDS FHL
inst. – instant (Latin), of the current month
IOF – Independent Order of Foresters
IOGT – Independent Order of Good Templars
IOJD – International Order of Job’s Daughters (freemason)
IOOF – Independent Order of Odd Fellows (fraternal organization)
IOR – Independent Order of Rechabites
IORG – International Order of the Rainbow for Girls (freemasonry)
IORM – Improved Order of Red Men
IOUAM – Improved Order of United American Mechanics