Middle English Frankeleyn, attested as a surname from late 12c., from Anglo-French fraunclein "freeholder, land-owner of free but not noble birth," from Old French franc "free" (see frank (adj.)); probably with the Germanic suffix also found in chamberlain.

The Franklin stove (1787) so called because it was invented by U.S. scientist/politician Benjamin Franklin (1706-1790). In early 19c., lightning rods often were called Franklins from his famous experiments with lightning in the 1750s.