Etymology
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stupid (adj.)

1540s, "mentally slow, lacking ordinary activity of mind, dull, inane," from French stupide (16c.) and directly from Latin stupidus "amazed, confounded; dull, foolish," literally "struck senseless," from stupere "be stunned, amazed, confounded," from PIE *stupe- "hit," from root *(s)teu- (1) "to push, stick, knock, beat" (see steep (adj.)). Related: Stupidly; stupidness.

Native words for this idea include negative compounds with words for "wise" (Old English unwis, unsnotor, ungleaw), also dol (see dull (adj.)), and dysig (see dizzy (adj.)). Stupid retained its association with stupor and its overtones of "stunned by surprise, grief, etc." into mid-18c. The difference between stupid and the less opprobrious foolish roughly parallels that of German töricht vs. dumm but does not exist in most European languages.

Men are born ignorant, not stupid; they are made stupid by education. [Bertrand Russell, paraphrasing Helvétius]
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stupe (n.)

"stupid person," 1762, shortening of stupid.

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stupor (n.)

late 14c., from Latin stupor "insensibility, numbness, dullness," from stupere "be stunned" (see stupid).

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stupefy (v.)

early 15c., from Latin stupefacere "make stupid or senseless, benumb, stun," from stupere "be stunned" (see stupid) + facere "to make, to do" (from PIE root *dhe- "to set, put").

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stupidity (n.)

1540s, "want of intelligence," from Latin stupiditatem (nominative stupiditas) "dullness, stupidity, senselessness," from stupidus "confounded, amazed; dull, foolish" (see stupid). It also at various times meant "lack of feeling or emotion" (1560s); "stupor, numbness" (c. 1600).

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stupendous (adj.)

1660s, correction of earlier stupendious "causing astonishment, astounding" (1540s), from Late Latin stupendus "to be wondered at," gerundive of Latin stupere "be stunned, be struck senseless, be aghast, astounded, or amazed" (see stupid). Related: Stupendously; stupendousness.

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masturbation (n.)
Origin and meaning of masturbation

"deliberate erotic self-stimulation," 1711 (earlier as mastupration, 1620s), from French masturbation and directly from Modern Latin masturbationem (nominative masturbatio), noun of action from past-participle stem of Latin masturbari "to masturbate."

The long-standing speculation is that this Latin word is altered (probably by influence of turbare "to disturb, confuse") from *manstuprare, from manu, ablative of manus "hand" (see manual) + stuprare "defile" (oneself), from stuprum "defilement, dishonor," related to stupere "to be stunned, stupefied" (see stupid). Hence the earliest form of the word in English. But perhaps the first element represents an unattested *mazdo- "penis" [OED]. An earlier technical word for this was onanism. Related: Masturbational.

Farmer and Henley ["Slang and Its Analogues," 1898] lists among the slang terms for "to masturbate" or "masturbation" frig (which they trace to Latin fricare "to rub") to bob; to box the Jesuit; to chuff, to chuffer; to claw; to digitate (of women); to fight one's turkey (Texan); to handle; to indorse; to milk; to mount a corporal and four; to dash one's doodle; and they note that it was "sometimes known as KEEPING DOWN THE CENSUS."

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dumb-ass (n.)

also dumbass, "stupid, ineffectual person," by 1959, from dumb (adj.) "stupid" + ass (n.2).

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jolt-head (n.)

"a stupid head," 1530s; later also "a big, clumsy, stupid person." The origin and signification of jolt here is unknown.

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