Cakka: 'wheel', is one of the seven 'precious possessions' ratana of a righteous World Emperor cakkavatti'He who owns the Wheel,' cf. D. 26, and symbolizes conquering progress and expanding sovereignty. From that derives the figurative expression dhamma-cakkam pavatteti, he sets rolling the Wheel of the Law' and the name of the Buddha's first sermon, Dhammacakkappavattana Sutta.
Another figurative meaning of C. is 'blessing'. There are 4 such 'auspicious wheels' or 'blessings': living in a suitable locality, company of good people, meritorious acts done in the past, right inclinations A. IV, 31.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.