The evidence for a god Ing is sporadic at best. What information we have is far from conclusive especially when what considerings whether Ing and Freyr are the same deity. The earliest hint of the deity is in Pliny’s Natural History (IV.99). Here he lists as one of five confederations of Germanic tribes the Ingvaeones. The name Ingvaeones is thought to mean “friends of Ing.” Tacitus takes it one step farther giving us a bit of myth to go with the name:
In their ancient songs, their only way of remembering or recording the past they celebrate an earth-born god Tuisco, and his son Mannus, as the origin of their race, as their founders. To Mannus they assign three sons, from whose names, they say, the coast tribes are called Ingaevones; those of the interior, Herminones; all the rest, Istaevones.
This myth parallels one in Hindu myth, Manu is said to have had two sons and three daughters, and to have been the ancestor of all mankind. One myth attributed to him is saving Mankind from a great flood. He is seen as the first king in the history of Mankind. The similarity is uncanny, and seems to indicate a common Indo-European origin for a God named Man.
The tale in Germania is not the only shell of a myth in regards to Ing. He is also mentioned in the Anglo-Saxon Rune Poem, his name being the name of one of the runes:
Ing wæs ærest mid Est-Denum
Gesewen secgum, oth he siddan eft
Ofer wæg gewat; wæn fter ran;
Thus heardingas thone hæle nemdun
Ing was first – among the East Danes
Seen by men – but he since went eft (back)
Over the wet way – his wain (wagon) ran after
Thus the Heardings – named the hero
Here Ing is listed as a hero and not a deity. However, this may be a change created by a Christian scribe and not lore per se. Too, it could be as a tribal ancestor he is thought to be a hero as well as a deity. Ing is also potentially named in the kings list of Bernicia where an Ingui is listed. It is possible that like Woden for the Mercian line he as seen as ancestor of the entire line before later additions.
The God Freyr was called Yngvi Freyr by the Swedes, and their kings were thought to descend from him. Here we are faced with a controversy, was Ing and Freyr seen as the same deity. In favor of this is the procession in a wain, as well as the name, and both are seen as ancestor deities. Against the two being one and the same are the differing fathers, Njord for Freyr and Mannus for Ing. It is possible that Mannus and Njord are one and the same. But then there is also the possibility that Njord was not considered Freyr’s father until late in Heathen Era. There is probably no real solution to the problem unless new evidence comes to light (such as a poem listing Mannus as Freyr’s father).
My own opinion is they are one and the same, and Njord as Freyr’s father was a late development. If we accept this most Norse myths can be attributed to Ing. It is a shame not more information on Ing survived so we could make a definite identification.