from The American Heritage® Dictionary of the English Language, 4th Edition
- suffix One that performs a specified action: accelerator.
- suffix State; quality; activity: valor.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- suffix Suffix appended to words to create an agent noun, indicating a person who does something.
from the GNU version of the Collaborative International Dictionary of English
- suffix A noun suffix denoting an act; a state or quality; as in error, fervor, pallor, candor, etc.
- suffix A noun suffix denoting an agent or doer; as in auditor, one who hears; donor, one who gives; obligor, elevator. It is correlative to -ee. In general -or is appended to words of Latin, and -er to those of English, origin. See -er.
Middle English -or, -our, from Old French -eor, -eur and Anglo-Norman -our, -ur, all from Latin -or, -ōr-.
Middle English -our, from Old French -eur, from Latin -or, -ōr-.(American Heritage® Dictionary of the English Language, Fourth Edition)