ignitor has the recorded history: A variant spelling of igniter, from ignite + -or. Ignite is from Latin ignire ('to set on fire'), from ignis ('fire'). Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the noun sense is "a device that ignites a fuel or charge; variant of igniter", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as ignite, ignition, and igniter. Its semantic neighborhood includes lighter, starter, detonator, and primer, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin ignis and Proto-Indo-European *hxngwnis.