graven (adj.)

"to engrave," Old English grafan "to dig, dig up; engrave, carve, chisel" (medial -f- pronounced as "v" in Old English; past tense grof, past participle grafen), from Proto-Germanic *grabanan (source also of Old Norse grafa "to dig; engrave; inquire into," Old Frisian greva, Dutch graven "to dig, delve," Old High German graban, German graben, Gothic graban "to dig, carve"), from the same source as grave (n.). Its Middle English strong past participle, graven, is the only part still active, the rest of the word supplanted by its derivative, engrave.

word-forming element making verbs (such as darken, weaken) from adjectives or nouns, from Old English -nian, from Proto-Germanic *-inojan (also source of Old Norse -na), from PIE adjectival suffix *-no-. Most active in Middle English and early modern English, hence most verbs in -en are comparatively recent.