Namaste Sri Jayashankar ji,
Very interesting post. One is reminded of the Mandukya Karika 4.86 and the bhashyam: Here the Bhashyam seems to take both the śama and dama to mean the same: upaśānti.
विप्राणां विनयो ह्येष शमः प्राकृत उच्यते ।
दमः प्रकृतिदान्तत्वादेवं विद्वाञ्शमं व्रजेत् ॥ ८६ ॥ 4.86
विप्राणां ब्राह्मणानां विनयः विनीतत्वं स्वाभाविकं यदेतदात्मस्वरूपेणावस्थानम् । एष विनयः शमोऽप्येष एव प्राकृतः स्वाभाविकः अकृतकः उच्यते । दमोऽप्येष एव प्रकृतिदान्तत्वात् स्वभावत एव चोपशान्तरूपत्वाद्ब्रह्मणः । एवं यथोक्तं स्वभावोपशान्तं ब्रह्म विद्वान् शमम् उपशान्तिं स्वाभाविकीं ब्रह्मस्वरूपां व्रजेत् ब्रह्मस्वरूपेणावतिष्ठत इत्यर्थः ॥
Here is the Swami Gambhirananda translation:
86. This is the modesty of the Brahmanas, this is called their natural tranquility, and this is their natural self-restraint resulting from spontaneous poise. Having known thus, one gets established in tranquility.
This continuance in the state of identity with the Self is the natural vinayah, modesty; viprānām, of the Brahmanas. This is their humility, and this is also ucyate, called; their prākrtah śamah, natural mental tranquility. Damah, self-restraint, too, is this only; prakrtidantatvat, because of (their) spontaneous poise, and because Brahman, too, is by nature quiescent. Evam vidvān, having known thus, having known the aforesaid Brahman as naturally tranquil; vrajet, one should attain; śamam, tranquility, which is spontaneous and which is the very nature of Brahman--that is to say one remains established in identification with Brahman.
warm regards
subbu