c. 1300, agheful "worthy of respect or fear, striking with awe; causing dread," from aghe, an earlier form of awe (n.), + -ful. The Old English word was egefull. Weakened sense "very bad" is from 1809; weakened sense of "excessively, very great" is by 1818. It formerly was occasionally used in a sense "profoundly reverential" (1590s).
Entries linking to awful
c. 1300, aue, "fear, terror, great reverence," earlier aghe, c. 1200, from a Scandinavian source, such as Old Norse agi "fright;" from Proto-Germanic *agiz- (source also of Old English ege "fear," Old High German agiso "fright, terror," Gothic agis "fear, anguish"), from PIE *agh-es- (source also of Greek akhos "pain, grief"), from root *agh- (1) "to be depressed, be afraid" (see ail). Current sense of "dread mixed with admiration or veneration" is due to biblical use with reference to the Supreme Being. To stand in awe (early 15c.) originally was simply to stand awe. Awe-inspiring is recorded from 1814.
Al engelond of him stod awe.
["The Lay of Havelok the Dane," c. 1300]
It is rare in Old English and Middle English, where full was much more commonly attached at the head of a word (for example Old English fulbrecan "to violate," fulslean "to kill outright," fulripod "mature;" Middle English had ful-comen "attain (a state), realize (a truth)," ful-lasting "durability," ful-thriven "complete, perfect," etc.).
an awful risk
the awful war
an awful voice
awful worshippers with bowed heads