Shatapatha Brahmana 6.7.1.18

6.7.1.18

yadvevainaṃ śikyena bibharti | saṃvatsara eṣo 'gnirṛtavaḥ śikyamṛtubhirhi saṃvatsaraḥ śaknoti sthātuṃ yacaknoti tasmācikyamṛtubhirevainametadbibharti ṣaḍudyāmam bhavati ṣaḍḍhyṛtavaḥ

And, again, why he carries him by means of a netting,--he, Agni, is the year, and the netting is the seasons; for by means of the seasons the year is able to exist, and inasmuch as it is so able (sak), therefore (the netting is called) 'sikya:' he thus carries him by the seasons. It is furnished with six strings, for there are six seasons.