unready adj.

prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").

The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.

It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.

Middle English redi, with adjectival suffix -i (as in busy, crafty, hungry, etc.) + Old English ræde, geræde "prepared, ready, suitably equipped;" of a horse, "ready for riding."

This is reconstructed to be from Proto-Germanic *(ga)raitha- "arranged" (source also of Old Frisian rede "ready," Middle Dutch gereit, Old High German reiti, Middle High German bereite, German bereit, Old Norse greiðr "ready, plain," Gothic garaiþs "ordered, arranged"), which is perhaps from PIE root *reidh- "to ride" (see ride (v.)).

Lengthened in Middle English by change of ending. Sense of "at hand, present, available" is late 12c. Of money, "immediately available," c. 1300, hence slang noun the ready "cash" (1680s). Phrase at the ready "in the position of a soldier's firearm after the command '(make) ready!'" is attested from 1837. As an adverb, c. 1300, "at hand." A ready-reckoner (1757) was a book of tabulated calculations of the sort used in ordinary business and housekeeping.

Middle English reden, ireden, "to counsel, advise," also "to read," from Old English rædan, gerædan (West Saxon), redan, geredan (Anglian) "to advise, counsel, persuade; discuss, deliberate; rule, guide; arrange, equip; forebode; to read (observe and apprehend the meaning of something written), utter aloud (words, letters, etc.); to explain; to learn through reading; to put in order."

This is reconstructed to be from Proto-Germanic *redan, source also of Old Norse raða, Old Frisian reda, Dutch raden, Old High German ratan, German raten "to advise, counsel, interpret, guess," from PIE root *re- "to reason, count."

Cognate words in most modern Germanic languages still mean "counsel, advise" (compare rede). Old English also had a related noun ræd, red "advice," and read is connected to riddle (n.1) via the notion of "interpret." Century Dictionary notes that the past participle should be written red, as it formerly was, and as in lead/led. Middle English past participle variants include eradde, irad, ired, iræd, irudde.  

The sense-transference to "interpret and understand the meaning of written symbols" is said to be unique to English and (perhaps under Old English influence) Old Norse raða. Most languages use a word rooted in the idea of "gather up" as their word for "read" (such as French lire, from Latin legere).

Sense of "make out the character of (a person)" is attested from 1610s. Musical sense of "perform (at first sight) from the notes" is by 1792. To read up "systematically study" is from 1842; read out (v.) "expel by proclamation" (Society of Friends) is from 1788. Read-only in computer jargon is recorded from 1961.