respectful adj.

late 14c., "relationship, relation; regard, consideration" (as in in respect to), from Old French respect and directly from Latin respectus "regard, a looking at," literally "act of looking back (or often) at one," noun use of past participle of respicere "look back at, regard, consider," from re- "back" (see re-) + specere "look at" (from PIE root *spek- "to observe").

Meanings "feeling of esteem excited by actions or attributes of someone or something; courteous or considerate treatment due to personal worth or power." From late 15c. as "an aspect of a thing, a relative property or quality," hence "point, detail, particular feature" (1580s). With all due respect as a polite phrase introducing deferential disagreement is attested by 1670s.

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.).

"showing disrespect, wanting in respect; irreverent, uncivil," 1670s; see dis- + respectful. Related: Disrespectfully; disrespectfulness.