early 13c., "full of dread or fear, timid," from dread (n.) + -ful. Meaning "causing dread, exciting terror" is from c. 1200; weakened sense of "very bad" is by 1680s. Related: Dreadfully; dreadfulness.
Entries linking to dreadful
dread v.
late 12c., "to fear very much, be in shrinking apprehension or expectation of," a shortening of Old English adrædan, contraction of ondrædan "counsel or advise against," also "to dread, fear, be afraid," from ond-, and- "against" (the same first element in answer, from PIE root *ant-) + rædan "to advise" (from PIE root *re- "to reason, count"). Cognate of Old Saxon andradon, Old High German intraten. Related: Dreaded; dreading.
As a noun from c. 1200, "great fear or apprehension; cause or object of apprehension." As a past-participle adjective (from the former strong past participle), "dreaded, frightful," c.1400; later "held in awe" (early 15c.).
-ful
word-forming element attached to nouns (and in modern English to verb stems) and meaning "full of, having, characterized by," also "amount or volume contained" (handful, bellyful); from Old English -full, -ful, which is full (adj.) become a suffix by being coalesced with a preceding noun, but originally a separate word. Cognate with German -voll, Old Norse -fullr, Danish -fuld. Most English -ful adjectives at one time or another had both passive ("full of x") and active ("causing x; full of occasion for x") senses.
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.).