decal n.

active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.

As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.

"heel-bone," 1751, from Latin (os) calcaneum "bone of the heel," from calcem (nominative calx (1)) "heel," a word of uncertain origin, perhaps from Etruscan. De Vaan lists as possible cognates Old Prussian culczi "hip," Lithuanian kulkšnis "ankle-(bone)," Bulgarian kalka "hip, thigh." Related: Calcaneal.

"mixed-up, ridiculous, implausible," American English slang word attested by 1946, popularized c. 1960, but said to be New York City children's slang from mid-1920s; perhaps an alteration of decalcomania (see decal). There is a 1945 recorded use of the word apparently meaning a kind of temporary tattoo used by children.