loco

A Spanish word that has entered English slang is loco - "crazy." The Online Etymology Dictionary provides the following origin:

"mad, crazy," 1844, American English, from Spanish loco (adj.) "insane," of uncertain origin, perhaps from Arabic lauqa, fem. of 'alwaq "fool, crazy person."

The American Heritage Dictionary goes a bit further in their entry for the Semitic root lwq:

 Arabic root, to soften. loco, perhaps from Arabic lawqā, feminine singular of alwaq, bent, foolish, from lāqa, to soften.

Could this Arabic root have a Hebrew cognate? I believe there might be one.

Post-biblical Hebrew has the root לקה, meaning "to strike, to flog." The biblical equivalent is נכה - "to best, strike." The root לקה gives us the noun מלקות malkut (sometimes pronounced malkot) for "punishment by lashes," whereas the root נכה provides מכה maka, in plural מכות makkot. This last word is the name of the Talmudic tractate Makkot, which deals with the laws of punishment by lashes, and within it frequently uses the synonym malkot. (For more on the confusion between the two terms, see here.)

However, this is not the only meaning of לקה. Klein offers the following meanings: "to be stricken, be smitten, be flogged, be scourged; to be affected with disease; to be eclipsed." (This last meaning gives us the Hebrew term for "eclipse" - ליקוי likui.) 

In his Arukh HaShalem, Kohut writes that the essence of the root means "to be softened, beaten," and mentions the Arabic root that means "to soften." So it seems we have our cognate. As proof, The Arukh (the dictionary published about 800 years earlier upon which Kohut wrote his supplement) quotes a Talmudic passage (Yevamot 80b), which mentions someone who has שער לקוי se'ar lakui. The Arukh says that means he has "soft hair" (and Rashi agrees in his commentary.)

For some reason, there are many fast food restaurants called El Pollo Loco, including Israeli equivalents. While they say it means "crazy chicken," I think "softened chicken" actually sounds more appetizing...