cruciform (adj.)

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.

c. 1200, forme, fourme, "semblance, image, likeness," from Old French forme, fourme, "physical form, appearance; pleasing looks; shape, image; way, manner" (12c.), from Latin forma "form, contour, figure, shape; appearance, looks; a fine form, beauty; an outline, a model, pattern, design; sort, kind condition," a word of unknown origin. One theory holds that it is from or cognate with Greek morphe "form, beauty, outward appearance" (see Morpheus) via Etruscan [Klein].

From c. 1300 as "physical shape (of something), contour, outline," of a person, "shape of the body;" also "appearance, likeness;" also "the imprint of an object." From c. 1300 as "correct or appropriate way of doing something; established procedure; traditional usage; formal etiquette." Mid-14c. as "instrument for shaping; a mould;" late 14c. as "way in which something is done," also "pattern of a manufactured object." Used widely from late 14c. in theology and Platonic philosophy with senses "archetype of a thing or class; Platonic essence of a thing; the formative principle." From c. 1300 in law, "a legal agreement; terms of agreement," later "a legal document" (mid-14c.). Meaning "a document with blanks to be filled in" is from 1855. From 1590s as "systematic or orderly arrangement;" from 1610s as "mere ceremony." From 1550s as "a class or rank at school" (from sense "a fixed course of study," late 14c.). Form-fitting (adj.) in reference to clothing is from 1893.