The now common Grinnell spelling was popularized in the mid-late eighteenth century. As members of the Grinnell family spread throughout the New World, town clerks spelled the name pretty much the way it sounded to them. Illiteracy was rampant, and the town clerks were often the most literate persons in many communities. Widespread literacy in America only came as a result of the Industrial Revolution, beginning in the 1840s, when factory operators required a more literate workforce to operate the new machines of the day. Only then did the Grinnell surname spelling truly stabilize. The spelling variations (at least those known to the Grinnell Family Association) appear below:

Grenelle, Grannel, Greanold, Greenable, Greenal, Greenell, Greenhill, Greenill, Greenold, Grenal, Grenale, Grenald, Greneal, Greneel, Grenel, Grenell, Grenhill, Grenill, Grennal(l), Grennel(l), Grennels, Grennil, Grennill, Grennold, Grennoll, Grenwell, Grenold, Grenolds, Grenoll, Grenow, Greonull, Grenull, Grenwell, Grinal(l), Grinals, Grindle, Grineal, Grinel, Grinell, Grinels, Grinill, Grinnall, Grinnald, Grinnalds, Grinnals, Grinnel, Grinnell, Grinnelly, Grinnels, Grinniel, Grinnol, Grinnold, Grinnolds, Grinnoll, Grinol, Grinold, Grinolds, Grinols, Grinrell, Grinwell, Gririnell, Grunell, Grunnell, Gueenall, Guenall, Guennell, Guinal, Gunel, Gunell, Gunnall, Gunnell, Gurnell, Grinslell