When Rivka told Yaakov that he should pretend to be Esav so that Yitzchak would bless him, Yaakov protested that Esav’s skin was hairy while his was smooth, chalak (Genesis 27:11).
“Chalak” can also denote something slippery as well as the act of slipping. Along these lines, in Rabbinic Hebrew, a chaluk is a plain, smooth garment with no frills.
The Targumim on Genesis 27:11 translate “chalak” as “shiiya.” It would thus appear that “shiya” is merely the Aramaic word for “chalak.” However, in his work Tirgem Avraham, the Vilna Gaon’s son, R. Avraham Vilner (1765-1808) argues that “shiiya” is actually a Hebrew word as well.
He points to Yechezkel comparing G-d’s redemption of the Jews from Egypt to a benevolent stranger taking in a baby girl. In describing the baby’s initial abandonment, Yechezkel says, “You were not washed with water for mishi” (Ezekiel 16:4). (“Mishi” shares its shin-ayin root with “shiiya.”) The Radak (in his commentary to Ezekiel and in Sefer HaShorashim) explains that “mishi” means smoothness as bathing in water causes one’s skin to become smooth.
If “shiya” is a Hebrew word, what’s the difference between it and “chalak”?
The answer lies in a close analysis of the prohibition of shaatnez. The Mishnah (Kilayim 9:8) states that “shaatnez” is a contraction of “shua” (smoothed), “tavui” (spun), and “nuz” (woven or twisted) – which alludes to the fact that the prohibition only applies to fabric made of wool and linen via these three processes.
Rashi (to Yevamos 5b) explains that “shua” is a cognate of “shiiya” and means combing smooth. He maintains the shaatnez prohibition only applies if wool and linen fibers were combed smooth together. If wool and linen were mixed at a later stage, the resulting thread or fabric is not shaatnez.
Tosafos, however, cites opinions that maintain that wool and linen that were processed separately and later attached does, in fact, constitute shaatnez. One practical ramification of this dispute is the legal status of felt made of wool and linen. Felt is made by pressing various fibers together into one textile. According to Rashi, it isn’t shaatnez because the wool and linen were not combed smooth together, but according to the opinions cited in Tosafos, it is. Evidently, these authorities define “shua” differently. Instead of meaning make smooth, they believed it means becoming smooth as a result of attaching multiple things.
From where is this definition of “shua” derived?
Rabbi Yaakov Tzvi Mecklenburg (1785-1865) points to Maimonides’ commentary to Kilayim 9:8, which defines “shua” by citing the Targum to Leviticus 14:42. In that verse, the Torah states that if the stones of one’s home are afflicted with tzaraas, one should remove the affected stones, replace them with other stones, and bring new mortar “and plaster the house.” The verb for plastering is “ve’tach,” which Targum Onkelos translates as “ve’yeshua.” In this context, “shua” clearly does not mean “making smooth,” but rather “applying plaster” (smoothed over a wall, which results in a smooth wall).
Rabbi Mecklenburg notes that another cognate, “sha,” means “closing one’s eyes” (Isaiah 6:10 and 32:3) since when a person closes his eyes, it appears as though he attaches his upper eyelid to his lower one. Thus, we have another source for shua meaning attachment.
Rabbi Mecklenburg writes that the shin-ayin root also serves as the core of “sha’ashua” (delight, enjoyment). He explains the connection by noting that feeling something smooth is an enjoyable sensory experience. Thus, the root meaning smooth is borrowed to refer to anything enjoyable. (In contrast to the other commentators mentioned above, Menachem ibn Saruk and Rashi explain that “mishi” is related to “sha’ashua,” and in the context of Yechezkel’s prophecy refers to bathing for enjoyment.)
The Yiddish/German word for “chalak” is “glatt.” That term is most famously used to refer to the halachic stringency that requires an animal’s lungs to be smooth. It is a cognate of the Yiddish/German “gleiten”/“glitchen,” which is a relative of the English word “glide.” The relationship between smooth and glide is obvious: one can easily glide on a smooth surface.
“Glitchen” has found its way into some familiar English words, such as (according to some linguists) “glitch” (which is a slip up). Etymologists even trace “gladness” (the feeling one has when life is sailing along smoothly) to this Germanic root.
In Modern Hebrew, surfing, skiing, or sliding down a slide in a children’s playground is called “glisha,” which is also derived from “glatt”/“glitch.” (Since Hebrew doesn’t have the itch-sound, that sound morphs into a sh-sound, such that “glitch” becomes “glish”).