1540s, "expressing reproach," also "worthy of reproach, shameful," from reproach (n.) + -ful. Related: Reproachfully; reproachfulness.
Entries linking to reproachful
reproach n.
mid-14c., reproche, "a rebuke, blame, censure" directed against a person; also "object of scorn or contempt;" c. 1400, as "disgrace, state of disgrace," from Anglo-French repruce, Old French reproche "blame, shame, disgrace" (12c.), from reprochier "to blame, bring up against."
OED cites Diez for the explanation that this is from Vulgar Latin *repropiare, from Latin re- "opposite of" + prope "near" (see propinquity), with suggestions of "bring near to" as in modern get in (someone's) face. But it points out other etymologists of French would have it from *reprobicare, from Latin reprobus/reprobare "disapprove, reject, condemn" (see reprobate (adj.)).
-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.).