1Of a person: having a full or plump face. Also (occasionally) in extended use.
2Of the moon: full.
3More generally: having the face turned directly to face the viewer or the person being looked at; having all the face visible.
Of a letter (especially a capital letter): having a face which occupies most or all of the type body; (sometimes) bold. Of a typeface, font, etc.: consisting of such letters. Now chiefly US (in later use especially with reference to titling fonts).
Mid 16th century; earliest use found in Richard Grafton (c1511–1573), printer and historian. From full + faced.