"that may be (lawfully) expressed in words," 1630s, from French effable or directly, from Latin effabilis "utterable," from effari "to utter" (see ineffable). Now obsolete or archaic.
Entries linking to effable
ineffable adj.
late 14c., "beyond expression, too great for words, inexpressible," from Old French ineffable (14c.) or directly from Latin ineffabilis "unutterable," from in- "not, opposite of" (see in- (1)) + effabilis "speakable," from effari "utter," from assimilated form of ex "out" (see ex-) + fari "to say, speak," from PIE root *bha- (2) "to speak, tell, say."
Meaning "that may not be spoken" is from 1590s. Plural noun ineffables was, for a time, a jocular euphemism for "trousers" (1823; see inexpressible). Related: Ineffably.