Origin and history of excruciate

1814, "a cross," from Latin crux "cross," a word of uncertain origin. Sometimes said to be cognate with Irish cruach "heap, hill," Gaulish *krouka "summit," Old Norse hryggr "backbone," Old English hrycg "back." But de Vaan is suspicious:

The Celtic and Gm. forms are often reconstructed as *kr(e)u-k-, but we find vacillating vocalism within Gm.; also, the meanings 'backbone' and 'heap' are not necessarily connected. Even if the words in *kruk- from Latin and Italo-Celtic belong together, the root structure does not look PIE (and a root enlargement k is unknown), and might be interpreted as a non-IE substratum word borrowed into Italo-Celtic. But Latin may also just have borrowed the word from a contemporary language.

The figurative use for "a central difficulty" (1718) is older in English than the literal sense; perhaps it is from Latin crux interpretum "a point in a text that is impossible to interpret," the literal meaning of which is something like "crossroads of interpreters." But Century Dictionary ascribes it to "the cross as an instrument of torture; hence anything that puzzles or vexes in a high degree ...." Extended sense of "central point" is attested by 1888.

"extremely painful," 1590s, present-participle adjective from excruciate. Related: Excruciatingly.

word-forming element, in English meaning usually "out of, from," but also "upwards, completely, deprive of, without," and "former;" from Latin ex "out of, out from the interior of a thing" (in opposition to in), "from within; from which time, since; according to; in regard to." This is reconstructed to be from PIE *eghs "out" (source also of Gaulish ex-, Old Irish ess-, Old Church Slavonic izu, Russian iz). In some cases also from Greek cognate ex, ek.

Often reduced to e- before -b-, -d-, -g-, consonantal -i-, -l-, -m-, -n-, -v- (as in elude, emerge, evaporate, etc.).

The sense in Latin naturally tended toward "thoroughly, utterly," and in some English ex- words with no clear connection to the idea of "out of," the element might be purely intensive. Among them are exhort, exhilarate, evident, excruciate, exclaim, exuberant, exaggerate, expiate, expect.

For use of Latin ex- as "(rise) up out of," as preserved in English emerge, emend, the notion is "out from the interior of a thing," in opposition to in-. Hence also in Latin, "in an upward direction," as in effervesce, exult, extol.

PIE *eghs had comparative form *eks-tero and superlative *eks-t(e)r-emo-.