Hello,

 

I am not sure if there is a ‘traditional’ etymological explanation, but here is a back of an envelope note.

 

The older lexicons [ Amara, Halāyudha, Śāśvata etc]. don’t attest these senses, but Keśavasvāmin and Hemacandra have some relevant entries. I don’t included later lexicons since their entries are mostly derivative.

 

tantraṃ svarāṣṭravyāpāre tantuvāne paricchade // 25cd //

(Nānārthārṇavasaṃkṣepa_Keśavasvāmin, Dvyakṣarakāṇḍaḥ, Napuṃsakaliṅgādhyāyaḥ, , 25, 0035)

 

tantraṃ svarāṣṭracintā syād āvāpas tv aricintanam / 715 ab /

(Abhidhānacintāmaṇi_Hemacandra, Martyakāṇḍaḥ,  715, 0030)

 

kaṭakaṃ dhvajinī tantraṃ daṇḍo 'nīkaṃ patākinī /

 varūthinā camūś cakraṃ skandhavāro 'sya tu sthitiḥ // 746 //

(Abhidhānacintāmaṇi Hemacandra, Martyakāṇḍaḥ, 746, 0031)

 

tantraṃ siddhānte rāṣṭre ca paracchandapradhānayoḥ // 413ab //

(Anekārthasaṅgraha_Hemacandra, Dvisvarakāṇḍaḥ, Dvisvararāntāḥ, , 413, 1)

 

 

If tantra has the meaning of bind → control → administrate, as attested in words such as svatantra and paratantra, it stands to reason that it extends to the agent par excellence of control and administration i.e. the state (rāṣṭre ca). Similarly, the meanings ‘matters concerning one’s territory’ i.e. defense (svarāṣṭracintā, svarāṣṭravyāpāra), and army (kaṭakaṃ dhvajinī etc.) seem to be tenable metonyms for tantra meaning the kingdom/state.

 

Best regards,

Naresh Keerthi

Department of Sanskrit Studies

Ashoka University, New Delhi