Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.2.11

3.2.2.11

yajñena vai devāḥ | imāṃ jitiṃ jigyuryaiṣāmiyaṃ jitiste hocuḥ kathaṃ na idam manuṣyairanabhyārohyaṃ syāditi te yajñasya rasaṃ dhītvā yathā madhu madhukṛto nirdhayeyurviduhya yajñaṃ yūpena yopayitvā tiro 'bhavannatha yadenenāyopayaṃstasmādyūpo nāma

By means of the sacrifice the gods gained that supreme authority which they now wield. They spake, 'How can this (world) of ours be made unattainable to men?' They sipped the sap of the sacrifice, even as bees would suck out honey; and having drained the sacrifice and scattered it by means of the sacrificial post, they disappeared. And because they scattered (yopaya) therewith, therefore it is called yûpa (post).