窈窕

First syllable 窈 (OC *qiːwʔ, “deep, dim”) is probably cognate to 幽 (OC *qɯw, “dark”); second syllable 窕 (OC *l'eːwʔ, “to bore, to perforate”) is probably related to 竅 (OC *kʰleːwɢs, “hole”) (Schuessler, 2007)

窈窕

1. (literary, of a woman) quiet and elegant; graceful and fair; gentle and beautiful

   • 窈窕淑女，君子好逑。 [Pre-Classical Chinese, trad. and simp.]

     From: The Classic of Poetry, c. 11^th – 7^th centuries BCE, translated based on James Legge's version

     Yǎotiǎo shūnǚ, jūnzǐ hǎoqiú. [Pinyin]

     The modest, retiring, virtuous, young lady:
     For our prince a good mate she.

2. (literary, of a woman) seductive; flirtatious
3. (literary) deep; secluded; profound

   • 或命巾車，或棹孤舟。既窈窕以尋壑，亦崎嶇而經丘。 [Literary Chinese, trad.]
     或命巾车，或棹孤舟。既窈窕以寻壑，亦崎岖而经丘。 [Literary Chinese, simp.]

     From: Tao Yuanming, 《歸去來辭》 "Verses on Returning"

     Huò mìng jīnchē, huò zhào gūzhōu. Jì yǎotiǎo yǐ xún hè, yì qíqū ér jīng qiū. [Pinyin]

     I either called covered wagons, or rowed lonely boats; already following gullies deep, then crossing hills rough.