1570s, "a thing made fraudulently," from forge (v.) + -ery. Meaning "act of counterfeiting" is 1590s. The literal sense of the verb tended to go with forging (late 14c. as "act of working on a forge," 1858 as "piece of work made on a forge").
forfend
forgat
forgave
forge
forger
forgery
forget
forgetful
forget-me-not
forgettable
forgivable