Origin and history of clammy

Old English clæg "stiff, sticky earth; clay," from Proto-Germanic *klaijaz (source also of Old High German kliwa "bran," German Kleie, Old Frisian klai, Old Saxon klei, Middle Dutch clei, Danish klæg "clay;" also Old English clæman, Old Norse kleima, Old High German kleiman "to cover with clay").

Some sources see these as being from a common PIE root meaning "slime; glue" also forming words for "clay" and verbs for "stick together." Compared words include Latin gluten "glue, beeswax;" Greek gloios "sticky matter;" Lithuanian glitus "sticky," glitas "mucus;" Old Church Slavonic glina "clay," glenu "slime, mucus;" Old Irish glenim "I cleave, adhere;" Old English cliða "plaster." But Beekes writes that "Not all comparisons are convincing," and notes that most words cited are from Balto-Slavic or Germanic, "which suggests European substrate origin."

In Scripture, the stuff from which the body of the first man was formed; hence "human body" (especially when dead). As an adjective, "formed of clay," 1520s. Clay-pigeon "saucer of baked clay used as a flying target in trap-shooting," in place of live birds, is from 1881. Feet of clay "fundamental weakness" is from Daniel ii.33.

very common adjective suffix, "full of, covered with, or characterized by" the thing expressed by the noun, Middle English -i, from Old English -ig, from Proto-Germanic *-iga-, from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Germanic cognates include Dutch, Danish, German -ig, Gothic -egs.

It was used from 13c. with verbs (drowsy, clingy), and by 15c. with other adjectives (crispy). Chiefly with monosyllables; with more than two the effect tends to become comedic.

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Variant forms in -y for short, common adjectives (vasty, hugy) helped poets after the loss of grammatically empty but metrically useful -e in late Middle English. Verse-writers adapted to -y forms, often artfully, as in Sackville's "The wide waste places, and the hugy plain." (and the huge plain would have been a metrical balk).

After Coleridge's criticism of it as archaic artifice, poets gave up stilly (Moore probably was last to make it work, with "Oft in the Stilly Night"), paly (which Keats and Coleridge himself had used) and the rest.

Jespersen ("Modern English Grammar," 1954) also lists bleaky (Dryden), bluey, greeny, and other color words, lanky, plumpy, stouty, and the slang rummy. Vasty survives, he writes, only in imitation of Shakespeare; cooly and moisty (Chaucer, hence Spenser) he regards as fully obsolete. But in a few cases he notes (haughty, dusky) they seem to have supplanted shorter forms.